diff --git a/day7/README.md b/day7/README.md
new file mode 100644
index 0000000..398782a
--- /dev/null
+++ b/day7/README.md
@@ -0,0 +1,128 @@
+# Day 7: No Space Left On Device
+
+You can hear birds chirping and raindrops hitting leaves as the expedition proceeds. Occasionally, you can even hear
+much louder sounds in the distance; how big do the animals get out here, anyway?
+
+The device the Elves gave you has problems with more than just its communication system. You try to run a system update:
+
+```shell
+$ system-update --please --pretty-please-with-sugar-on-top
+Error: No space left on device
+```
+
+Perhaps you can delete some files to make space for the update?
+
+You browse around the filesystem to assess the situation and save the resulting terminal output (your puzzle input). For
+example:
+
+``` shell
+$ cd /
+$ ls
+dir a
+14848514 b.txt
+8504156 c.dat
+dir d
+$ cd a
+$ ls
+dir e
+29116 f
+2557 g
+62596 h.lst
+$ cd e
+$ ls
+584 i
+$ cd ..
+$ cd ..
+$ cd d
+$ ls
+4060174 j
+8033020 d.log
+5626152 d.ext
+7214296 k
+```
+
+The filesystem consists of a tree of files (plain data) and directories (which can contain other directories or files).
+The outermost directory is called `/`. You can navigate around the filesystem, moving into or out of directories and
+listing the contents of the directory you're currently in.
+
+Within the terminal output, lines that begin with `$` are **commands you executed**, very much like some modern
+computers:
+
+- `cd` means **change directory**. This changes which directory is the current directory, but the specific result
+  depends on the argument:
+    - `cd x` moves in one level: it looks in the current directory for the directory named x and makes it the current
+      directory.
+    - `cd ..` moves **out** one level: it finds the directory that contains the current directory, then makes that
+      directory the current directory.
+    - `cd /` switches the current directory to the outermost directory, `/`.
+- `ls` means **list**. It prints out all the files and directories immediately contained by the current directory:
+    - `123 abc` means that the current directory contains a file named `abc` with size `123`.
+    - `dir xyz` means that the current directory contains a directory named `xyz`.
+
+Given the commands and output in the example above, you can determine that the filesystem looks visually like this:
+
+```shell
+- / (dir)
+    - a (dir)
+        - e (dir)
+            - i (file, size=584)
+        - f (file, size=29116)
+        - g (file, size=2557)
+        - h.lst (file, size=62596)
+    - b.txt (file, size=14848514)
+    - c.dat (file, size=8504156)
+    - d (dir)
+        - j (file, size=4060174)
+        - d.log (file, size=8033020)
+        - d.ext (file, size=5626152)
+        - k (file, size=7214296)
+```
+
+Here, there are four directories: `/` (the outermost directory), `a` and `d` (which are in `/`), and `e` (which is in
+`a`). These directories also contain files of various sizes.
+
+Since the disk is full, your first step should probably be to find directories that are good candidates for deletion. To
+do this, you need to determine the **total size** of each directory. The total size of a directory is the sum of the
+sizes of the files it contains, directly or indirectly. (Directories themselves do not count as having any intrinsic
+size.)
+
+The total sizes of the directories above can be found as follows:
+
+- The total size of directory `e` is **584** because it contains a single file `i` of size 584 and no other directories.
+- The directory `a` has total size **94853** because it contains files `f` (size 29116), `g` (size 2557), and `h.lst` (
+  size 62596), plus file `i` indirectly (`a` contains `e` which contains `i`).
+- Directory `d` has total size **24933642**.
+- As the outermost directory, `/` contains every file. Its total size is **48381165**, the sum of the size of every
+  file.
+
+To begin, find all of the directories with a total size of **at most 100000**, then calculate the sum of their total
+sizes. In the example above, these directories are a and e; the sum of their total sizes is **95437** (94853 + 584). (As
+in this example, this process can count files more than once!)
+
+Find all of the directories with a total size of at most 100000. **What is the sum of the total sizes of those
+directories?**
+
+## Part Two
+
+Now, you're ready to choose a directory to delete.
+
+The total disk space available to the filesystem is `70000000`. To run the update, you need unused space of at least
+`30000000`. You need to find a directory you can delete that will **free up enough space** to run the update.
+
+In the example above, the total size of the outermost directory (and thus the total amount of used space) is `48381165`;
+this means that the size of the **unused** space must currently be `21618835`, which isn't quite the `30000000` required
+by the update. Therefore, the update still requires a directory with total size of at least `8381165` to be deleted
+before it can run.
+
+To achieve this, you have the following options:
+
+- Delete directory `e`, which would increase unused space by `584`.
+- Delete directory `a`, which would increase unused space by `94853`.
+- Delete directory `d`, which would increase unused space by `24933642`.
+- Delete directory `/`, which would increase unused space by `48381165`.
+
+Directories `e` and `a` are both too small; deleting them would not free up enough space. However, directories `d`
+and `/` are both big enough! Between these, choose the **smallest**: `d`, increasing unused space by **24933642**.
+
+Find the smallest directory that, if deleted, would free up enough space on the filesystem to run the update.\
+**What is the total size of that directory?**
\ No newline at end of file
diff --git a/day7/__init__.py b/day7/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/day7/input.txt b/day7/input.txt
new file mode 100644
index 0000000..67a6e8b
--- /dev/null
+++ b/day7/input.txt
@@ -0,0 +1,967 @@
+$ cd /
+$ ls
+dir fcqv
+dir fcv
+72939 hdpgfcwd
+236918 jlncjqh.csz
+dir jvwfwrg
+dir tzwpllhq
+dir vglf
+28586 wzljr.zvp
+$ cd fcqv
+$ ls
+dir fhg
+277152 qldfrhm.qnr
+269351 qsd
+dir thbb
+$ cd fhg
+$ ls
+dir jljrdvw
+$ cd jljrdvw
+$ ls
+101940 vsvgjg.tpn
+$ cd ..
+$ cd ..
+$ cd thbb
+$ ls
+144311 cchngzcc.lcd
+178246 fbsj.wtl
+48521 gfsqtssb.vtg
+284713 jwl.hll
+96717 wdqqqv.pcr
+$ cd ..
+$ cd ..
+$ cd fcv
+$ ls
+dir ffhwwg
+275505 fprcz.hrd
+179689 jwn
+69265 tfnws.drt
+38365 twvt.dbs
+dir vcqsrw
+247592 zldbq
+dir znzpm
+$ cd ffhwwg
+$ ls
+dir hlqf
+$ cd hlqf
+$ ls
+30443 vrdbrwp.dss
+$ cd ..
+$ cd ..
+$ cd vcqsrw
+$ ls
+dir bzlnsjmv
+dir rvbtnz
+224487 slr
+255340 vrdbrwp.dss
+$ cd bzlnsjmv
+$ ls
+272548 qwqlzvzv
+$ cd ..
+$ cd rvbtnz
+$ ls
+165670 jwl.lhn
+$ cd ..
+$ cd ..
+$ cd znzpm
+$ ls
+dir mjwnsw
+$ cd mjwnsw
+$ ls
+219638 bzcb
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd jvwfwrg
+$ ls
+dir ffhwwg
+42104 hmphb.qvq
+dir hzjpg
+dir jwl
+dir nmz
+243217 qldfrhm.rws
+dir tdjtv
+dir wdn
+$ cd ffhwwg
+$ ls
+179995 hcbf.dhw
+176263 lgssjp.mnl
+$ cd ..
+$ cd hzjpg
+$ ls
+241535 ddlcslcs.zjh
+dir ddrwfq
+dir mqwww
+29329 qwqlzvzv
+91380 vrdbrwp.dss
+dir wctwz
+210633 wdqqqv.pcr
+dir wlrmbtdg
+172051 zldbq
+$ cd ddrwfq
+$ ls
+11756 ffhwwg
+$ cd ..
+$ cd mqwww
+$ ls
+149750 wlfmbv.cgp
+$ cd ..
+$ cd wctwz
+$ ls
+277720 qldfrhm.bph
+$ cd ..
+$ cd wlrmbtdg
+$ ls
+14154 ffhwwg
+dir hgdjv
+dir qldfrhm
+48920 qwqlzvzv
+101228 wdqqqv.pcr
+159676 zldbq
+$ cd hgdjv
+$ ls
+dir hlw
+$ cd hlw
+$ ls
+229687 cdzwfzww.wcv
+$ cd ..
+$ cd ..
+$ cd qldfrhm
+$ ls
+254189 nfbp.gcg
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd jwl
+$ ls
+277778 drtw
+dir ghgf
+dir gqlmq
+163875 jwl.pmm
+dir mjm
+dir qgq
+$ cd ghgf
+$ ls
+181540 zsgjptrm.thf
+$ cd ..
+$ cd gqlmq
+$ ls
+dir ffhwwg
+283989 hzpwn
+dir jwl
+dir pqdqntr
+62581 vrdbrwp.dss
+$ cd ffhwwg
+$ ls
+242533 qwqlzvzv
+21991 wdqqqv.pcr
+$ cd ..
+$ cd jwl
+$ ls
+179926 jfgbmb.qsd
+dir zjv
+$ cd zjv
+$ ls
+102693 ffhwwg.hrt
+$ cd ..
+$ cd ..
+$ cd pqdqntr
+$ ls
+159376 nqwcsdmv
+$ cd ..
+$ cd ..
+$ cd mjm
+$ ls
+273410 hdbmpnfv
+8169 qwqlzvzv
+87728 tfgq.vbt
+221237 vrdbrwp.dss
+$ cd ..
+$ cd qgq
+$ ls
+dir dgq
+dir hlw
+164971 jvwfwrg
+dir jwl
+158534 qftjvcz.pfv
+251561 qzzpmh
+282035 wsz
+$ cd dgq
+$ ls
+dir ffhwwg
+237291 nfqzn
+70142 qfnrvmp.vbb
+55607 zldbq
+$ cd ffhwwg
+$ ls
+117790 sqhrdmd.thc
+186465 tfctr.scc
+236863 wdqqqv.pcr
+$ cd ..
+$ cd ..
+$ cd hlw
+$ ls
+244567 wrnplfgg.pcw
+$ cd ..
+$ cd jwl
+$ ls
+105997 lpsg.jjl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nmz
+$ ls
+51802 qwqlzvzv
+128617 zldbq
+$ cd ..
+$ cd tdjtv
+$ ls
+dir jvwfwrg
+dir mdmwf
+dir rlpbrq
+$ cd jvwfwrg
+$ ls
+35406 wdqqqv.pcr
+$ cd ..
+$ cd mdmwf
+$ ls
+dir ffhwwg
+15609 rdpwqw.pfv
+205721 zldbq
+$ cd ffhwwg
+$ ls
+117473 hdcv.cwj
+$ cd ..
+$ cd ..
+$ cd rlpbrq
+$ ls
+120058 dgddvmt.fnv
+194704 ffhwwg
+256467 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd wdn
+$ ls
+170094 bzqsnv
+dir gqmghw
+150252 gwgz.fnf
+243953 jfgbmb.qsd
+123382 qwqlzvzv
+96220 wpc.swm
+dir ztqbhjr
+$ cd gqmghw
+$ ls
+dir tlgbcrh
+$ cd tlgbcrh
+$ ls
+281457 ztjhcrwf.ljf
+$ cd ..
+$ cd ..
+$ cd ztqbhjr
+$ ls
+271212 jfgbmb.qsd
+dir nbhq
+dir vfmmj
+260079 vrdbrwp.dss
+$ cd nbhq
+$ ls
+179096 hlw.hrh
+150184 wdqqqv.pcr
+$ cd ..
+$ cd vfmmj
+$ ls
+57445 hlw.pfb
+40329 qldfrhm
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd tzwpllhq
+$ ls
+33596 cmwwd
+16963 hlw.jrw
+161107 hlw.npq
+dir jwv
+152431 nqf.jjg
+dir qldfrhm
+dir swmwvl
+dir wzpth
+$ cd jwv
+$ ls
+dir bgswd
+188795 hlw
+dir jvwfwrg
+dir jwl
+dir mbcb
+dir qldfrhm
+30173 qwqlzvzv
+193577 zldbq
+$ cd bgswd
+$ ls
+dir hdgt
+216966 ldbg.dzh
+$ cd hdgt
+$ ls
+70441 fnv.bpl
+$ cd ..
+$ cd ..
+$ cd jvwfwrg
+$ ls
+dir mctsws
+69374 qldfrhm
+$ cd mctsws
+$ ls
+257337 qsgvbj
+$ cd ..
+$ cd ..
+$ cd jwl
+$ ls
+161061 ffhwwg
+$ cd ..
+$ cd mbcb
+$ ls
+dir fbhhq
+dir rgjwh
+$ cd fbhhq
+$ ls
+dir vnn
+$ cd vnn
+$ ls
+55629 cthtjm.wbt
+$ cd ..
+$ cd ..
+$ cd rgjwh
+$ ls
+7826 wrhpmqd.fvw
+$ cd ..
+$ cd ..
+$ cd qldfrhm
+$ ls
+14471 hlw.lwh
+163165 jnpgzcmt
+10880 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd qldfrhm
+$ ls
+dir ffhwwg
+dir jwl
+15164 ldmm
+188544 pwg.zsf
+255566 qjlggt
+dir tbngqwb
+59898 zldbq
+$ cd ffhwwg
+$ ls
+218749 ffhwwg.ztr
+$ cd ..
+$ cd jwl
+$ ls
+40245 cbhtl.frv
+268818 fmwvvg
+161866 nqp
+dir nsvjcpc
+dir nwdvblg
+171528 qldfrhm
+dir qqmb
+282266 wdqqqv.pcr
+$ cd nsvjcpc
+$ ls
+43660 wtnhh.zgw
+$ cd ..
+$ cd nwdvblg
+$ ls
+dir cltj
+dir fds
+$ cd cltj
+$ ls
+86970 dlzsw.whj
+111805 qwqlzvzv
+247438 zldbq
+$ cd ..
+$ cd fds
+$ ls
+49560 fsrvhv.lhd
+234970 jvwfwrg.pfd
+133376 qgbmc
+$ cd ..
+$ cd ..
+$ cd qqmb
+$ ls
+139542 qzm.jjz
+$ cd ..
+$ cd ..
+$ cd tbngqwb
+$ ls
+dir jwl
+273706 vcfmt.jqv
+76731 wdqqqv.pcr
+$ cd jwl
+$ ls
+45969 ltvvm
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd swmwvl
+$ ls
+32187 dzn.rnz
+dir gsj
+83763 jfgbmb.qsd
+93113 vrdbrwp.dss
+$ cd gsj
+$ ls
+dir fpzj
+152202 wntpsp.tbf
+$ cd fpzj
+$ ls
+83665 btwqdhnf.qwz
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd wzpth
+$ ls
+dir snhss
+$ cd snhss
+$ ls
+dir hlw
+$ cd hlw
+$ ls
+15123 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd vglf
+$ ls
+dir gdjmt
+dir hnnw
+dir htqzfcc
+dir nqf
+269558 qldfrhm
+116732 rqg.zbf
+dir tvmqzwmn
+72822 vrdbrwp.dss
+$ cd gdjmt
+$ ls
+214742 jfgbmb.qsd
+$ cd ..
+$ cd hnnw
+$ ls
+dir ffhwwg
+217384 jfgbmb.qsd
+153385 jvwfwrg
+dir jwl
+dir shdt
+143935 vrdbrwp.dss
+90319 zldbq
+101043 zqvwfhrz.rfz
+$ cd ffhwwg
+$ ls
+dir dsqwrdnq
+261158 jvwfwrg.plf
+$ cd dsqwrdnq
+$ ls
+129823 pngjr.rpg
+$ cd ..
+$ cd ..
+$ cd jwl
+$ ls
+dir bzq
+215828 hpqtdllh
+dir jjmndb
+dir pjzqjbd
+dir pmslv
+dir smfg
+dir wmjjwh
+$ cd bzq
+$ ls
+199534 jvwfwrg.tnt
+$ cd ..
+$ cd jjmndb
+$ ls
+dir cbfdqtc
+dir gnjlnz
+dir hlw
+201443 lgdvsvc.wvp
+dir lzlwstch
+175514 nlvh.rjc
+dir qldfrhm
+144450 qwqlzvzv
+dir ssh
+dir tbdhtqn
+150014 ttp.zqf
+240619 wdqqqv.pcr
+$ cd cbfdqtc
+$ ls
+39125 ffhwwg.fpg
+264178 jpnslr.qqt
+180897 wjmfvtvn
+$ cd ..
+$ cd gnjlnz
+$ ls
+217994 jwl.ddh
+$ cd ..
+$ cd hlw
+$ ls
+dir chgwjl
+dir dsz
+165192 ffhwwg.qfc
+40771 gzph.mvb
+46495 jvwfwrg
+122203 lhgfb.blq
+175167 qwqlzvzv
+dir ttr
+$ cd chgwjl
+$ ls
+284909 jwl.qqp
+$ cd ..
+$ cd dsz
+$ ls
+47411 bsshfjl.wbd
+$ cd ..
+$ cd ttr
+$ ls
+dir fgbgl
+dir qsflswrq
+5609 sfz
+250311 vrdbrwp.dss
+$ cd fgbgl
+$ ls
+203288 scclvct
+$ cd ..
+$ cd qsflswrq
+$ ls
+222611 ffhwwg
+143339 thrwtw.nsg
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd lzlwstch
+$ ls
+dir ffhwwg
+dir hwmzp
+dir jvwfwrg
+dir ndpbn
+dir qllzhd
+$ cd ffhwwg
+$ ls
+51165 hlw.hdn
+$ cd ..
+$ cd hwmzp
+$ ls
+54571 qwqlzvzv
+$ cd ..
+$ cd jvwfwrg
+$ ls
+130055 qldfrhm
+$ cd ..
+$ cd ndpbn
+$ ls
+160215 hptz.zms
+$ cd ..
+$ cd qllzhd
+$ ls
+41306 hwnllpw.vjp
+162845 vrdbrwp.dss
+$ cd ..
+$ cd ..
+$ cd qldfrhm
+$ ls
+dir bwcg
+dir ffhwwg
+$ cd bwcg
+$ ls
+181254 wpzpd
+$ cd ..
+$ cd ffhwwg
+$ ls
+240618 cdmlz.wsf
+dir ffhwwg
+201345 jfww
+128709 jwl.gwc
+284209 pswsrf.wwt
+dir qldfrhm
+$ cd ffhwwg
+$ ls
+13278 wcc.qmr
+165094 wdqqqv.pcr
+$ cd ..
+$ cd qldfrhm
+$ ls
+104797 ccgfmcnc.jrg
+273814 hlw.pnt
+182685 jvwfwrg.szl
+190595 stjhgqd
+dir stpvb
+105499 vbqw.vwc
+dir zldj
+$ cd stpvb
+$ ls
+221672 vrdbrwp.dss
+$ cd ..
+$ cd zldj
+$ ls
+dir jwl
+$ cd jwl
+$ ls
+130858 jhqhfrbp.nff
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ssh
+$ ls
+65814 jfgbmb.qsd
+dir jvwfwrg
+70744 zqhftjbs.jwd
+$ cd jvwfwrg
+$ ls
+212356 jfgf.szv
+$ cd ..
+$ cd ..
+$ cd tbdhtqn
+$ ls
+37228 ffhwwg.vvc
+69069 nrtgtbmp.qlv
+dir rmrwm
+166294 zldbq
+$ cd rmrwm
+$ ls
+118846 qldfrhm.hns
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pjzqjbd
+$ ls
+259092 cqlfdc.qdp
+89322 nmpvmdlp
+$ cd ..
+$ cd pmslv
+$ ls
+82637 jwl.lhz
+$ cd ..
+$ cd smfg
+$ ls
+dir gfbpcr
+dir sghtlzqv
+$ cd gfbpcr
+$ ls
+23958 hnpgr.htf
+$ cd ..
+$ cd sghtlzqv
+$ ls
+275943 jfgbmb.qsd
+149592 qwqlzvzv
+285215 sgptfc.msd
+179076 zldbq
+$ cd ..
+$ cd ..
+$ cd wmjjwh
+$ ls
+198333 jfgbmb.qsd
+59553 qwqlzvzv
+91883 wdqqqv.pcr
+7054 zldbq
+$ cd ..
+$ cd ..
+$ cd shdt
+$ ls
+27781 hlw.vcl
+255994 jpd
+dir mrgppm
+dir mwvgmjmb
+dir nsbrbcq
+263384 rbwbqf.qjc
+251640 tgr.rdc
+16959 zldbq
+$ cd mrgppm
+$ ls
+dir ghzhzzp
+dir jwl
+dir tgpm
+$ cd ghzhzzp
+$ ls
+dir bqplqq
+dir vtqgwsj
+$ cd bqplqq
+$ ls
+234131 lntldzhp
+$ cd ..
+$ cd vtqgwsj
+$ ls
+260109 qrzrfzr
+$ cd ..
+$ cd ..
+$ cd jwl
+$ ls
+112258 ffhwwg.wvp
+$ cd ..
+$ cd tgpm
+$ ls
+dir hlw
+167788 zldbq
+$ cd hlw
+$ ls
+70960 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd mwvgmjmb
+$ ls
+142087 pvpw.wtv
+$ cd ..
+$ cd nsbrbcq
+$ ls
+dir hljjp
+$ cd hljjp
+$ ls
+125853 jfgbmb.qsd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd htqzfcc
+$ ls
+dir cqs
+dir dsnpcnv
+dir ffhwwg
+90664 jfgbmb.qsd
+92316 lsjtfbvt
+dir mftm
+dir mmgn
+dir qqvzvw
+166400 qwqlzvzv
+dir vtf
+dir wrbwbdt
+$ cd cqs
+$ ls
+232548 nnv.wph
+35933 rwqj.crp
+$ cd ..
+$ cd dsnpcnv
+$ ls
+115805 ffhwwg.tvt
+$ cd ..
+$ cd ffhwwg
+$ ls
+dir qldfrhm
+dir wjj
+$ cd qldfrhm
+$ ls
+221567 qwqlzvzv
+dir rsztzjcm
+33248 vrdbrwp.dss
+114731 wdqqqv.pcr
+276521 zldbq
+$ cd rsztzjcm
+$ ls
+268313 frdpwjsh.wsh
+283644 jfgbmb.qsd
+dir jhdcdm
+84130 jvwfwrg.vsd
+31286 jwl.rth
+$ cd jhdcdm
+$ ls
+212461 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd wjj
+$ ls
+89758 jvwfwrg.mmg
+163105 vrdbrwp.dss
+$ cd ..
+$ cd ..
+$ cd mftm
+$ ls
+278389 bbth.bht
+$ cd ..
+$ cd mmgn
+$ ls
+28122 zldbq
+$ cd ..
+$ cd qqvzvw
+$ ls
+dir mjw
+dir qldfrhm
+dir zbmpdwtc
+$ cd mjw
+$ ls
+dir cvn
+dir dlgzc
+10631 jfgbmb.qsd
+206351 qldfrhm.hgf
+136824 qwqlzvzv
+116870 qwzczrcf
+$ cd cvn
+$ ls
+146142 ggtd.jlp
+$ cd ..
+$ cd dlgzc
+$ ls
+130120 wpc
+$ cd ..
+$ cd ..
+$ cd qldfrhm
+$ ls
+260238 bpf.jbv
+270180 cwdnf
+dir czwwzj
+50884 jvwfwrg.fmq
+dir mjpzgbww
+252028 qtdzw.bmb
+dir rzqj
+$ cd czwwzj
+$ ls
+dir cpwwqrph
+19863 jfgbmb.qsd
+dir snl
+83915 vrdbrwp.dss
+$ cd cpwwqrph
+$ ls
+dir jvwfwrg
+$ cd jvwfwrg
+$ ls
+176717 jfgbmb.qsd
+$ cd ..
+$ cd ..
+$ cd snl
+$ ls
+dir btngcvt
+dir ffhwwg
+53428 gchwbc.jtf
+220232 vrdbrwp.dss
+$ cd btngcvt
+$ ls
+172859 jwl.smp
+dir tgcqmbrn
+$ cd tgcqmbrn
+$ ls
+149905 jvwfwrg
+$ cd ..
+$ cd ..
+$ cd ffhwwg
+$ ls
+145399 qldfrhm.hbg
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd mjpzgbww
+$ ls
+52355 bwzwfjtc.rmn
+5856 ffhwwg.tnh
+146211 scbdnlgl
+$ cd ..
+$ cd rzqj
+$ ls
+dir jmjszd
+134481 vgr
+187382 vrdbrwp.dss
+$ cd jmjszd
+$ ls
+81971 qldfrhm
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zbmpdwtc
+$ ls
+193744 jvntrn
+231403 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd vtf
+$ ls
+2562 vzngcbq
+$ cd ..
+$ cd wrbwbdt
+$ ls
+dir brzwbmc
+29261 hlw
+$ cd brzwbmc
+$ ls
+dir ggh
+174287 jfgbmb.qsd
+dir jwl
+247329 mpdz
+dir thm
+83546 vrdbrwp.dss
+231269 wmwhhhmn.rms
+$ cd ggh
+$ ls
+dir cqrmsltg
+18724 mrlwwdv.ffb
+$ cd cqrmsltg
+$ ls
+dir ffhwwg
+dir jvwfwrg
+41263 pmrmh.zmn
+dir tcjr
+$ cd ffhwwg
+$ ls
+dir hlw
+$ cd hlw
+$ ls
+139875 ljnfchr.frr
+$ cd ..
+$ cd ..
+$ cd jvwfwrg
+$ ls
+141078 zldbq
+$ cd ..
+$ cd tcjr
+$ ls
+dir hnngpdc
+153685 jwl
+93502 nwlsf.dbq
+226658 qwqlzvzv
+$ cd hnngpdc
+$ ls
+243203 gchtc.sst
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd jwl
+$ ls
+62087 hfp.cfv
+$ cd ..
+$ cd thm
+$ ls
+228008 dfqgcd.frc
+167850 glblcw
+dir jvwfwrg
+$ cd jvwfwrg
+$ ls
+dir ffhwwg
+dir jgvf
+170488 qmc.vgf
+$ cd ffhwwg
+$ ls
+258985 jfgbmb.qsd
+$ cd ..
+$ cd jgvf
+$ ls
+150671 rdplqftl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nqf
+$ ls
+dir rglrpqd
+$ cd rglrpqd
+$ ls
+276785 nnbs.dhr
+224128 qwqlzvzv
+$ cd ..
+$ cd ..
+$ cd tvmqzwmn
+$ ls
+47655 jfgbmb.qsd
+233646 qwqlzvzv
+237245 rqfp
+185131 whntfvm.sfz
\ No newline at end of file
diff --git a/day7/main.py b/day7/main.py
new file mode 100644
index 0000000..47ca491
--- /dev/null
+++ b/day7/main.py
@@ -0,0 +1,115 @@
+from dataclasses import dataclass, field
+from typing import Self
+
+from common.file import read_data
+
+DIRECTORY = "directory"
+FILE = "file"
+
+test_data = [
+    "$ cd /",
+    "$ ls",
+    "dir a",
+    "14848514 b.txt",
+    "8504156 c.dat",
+    "dir d",
+    "$ cd a",
+    "$ ls",
+    "dir e",
+    "29116 f",
+    "2557 g",
+    "62596 h.lst",
+    "$ cd e",
+    "$ ls",
+    "584 i",
+    "$ cd ..",
+    "$ cd ..",
+    "$ cd d",
+    "$ ls",
+    "4060174 j",
+    "8033020 d.log",
+    "5626152 d.ext",
+    "7214296 k",
+]
+
+
+@dataclass
+class Node:
+    node_type: str
+    name: str
+    _size: int = 0
+    children: list[Self] = field(default_factory=list)
+    parent: Self | None = None
+
+    def add(self, leaf: Self):
+        leaf.parent = self
+        self.children.append(leaf)
+
+    @property
+    def size(self) -> int:
+        if self.node_type == DIRECTORY:
+            self.size = sum(child.size for child in self.children)
+        return self._size
+
+    @size.setter
+    def size(self, value: int):
+        self._size = value
+
+
+def new_leaf(command: str) -> Node:
+    a, b = command.split(" ")
+
+    if a == "dir":
+        node_type = DIRECTORY
+        name = b
+        size = 0
+    else:
+        node_type = FILE
+        name = b
+        size = int(a)
+
+    node = Node(node_type=node_type, name=name)
+    node.size = size
+    return node
+
+
+def move_to(tree: Node, directory: str) -> Node:
+    if directory == "..":
+        return tree.parent
+    return [node for node in tree.children if node.name == directory][0]
+
+
+def build_tree(data: list[str]) -> int:
+    root = Node(node_type=DIRECTORY, name="/")
+    current = root
+
+    directories = []
+
+    i = 1
+    while i < len(data[1:]):
+        if "$ cd" in data[i]:
+            _, _, directory = data[i].split(" ")
+            current = move_to(current, directory)
+            i += 1
+        if "$ ls" in data[i]:
+            i += 1
+            while i <= len(data[1:]) and data[i][0] != "$":
+                leaf = new_leaf(data[i])
+                if leaf.node_type == DIRECTORY:
+                    directories.append(leaf)
+                current.add(leaf)
+                i += 1
+    return sum(directory.size for directory in directories if directory.size < 100_000)
+
+
+def total_files_size(data: list[str]) -> int:
+    return build_tree(data)
+
+
+if __name__ == "__main__":
+    dataset = read_data()
+
+    res = total_files_size(test_data)
+    assert res == 95437, f"{res} is not the right value, want 95437"
+
+    print(total_files_size(dataset))