diff --git a/day07/common.rs b/day07/common.rs
new file mode 100644
index 0000000..7ece8eb
--- /dev/null
+++ b/day07/common.rs
@@ -0,0 +1,112 @@
+// Copyright 2022 Christian Ulrich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::io;
+use std::iter;
+
+#[derive(Debug)]
+pub enum Node {
+    Directory { name: String, children: Vec<Node> },
+    File { name: String, size: usize },
+}
+
+pub struct FileSystem {
+    root: Node,
+}
+
+impl Node {
+    pub fn name(&self) -> &str {
+        match self {
+            Node::File { name, size: _ } => name,
+            Node::Directory { name, children: _ } => name,
+        }
+    }
+
+    pub fn size(&self) -> usize {
+        match self {
+            Node::File { name: _, size } => *size,
+            Node::Directory { name: _, children } => {
+                children.iter().fold(0, |acc, c| acc + c.size())
+            }
+        }
+    }
+
+    pub fn walk(&self) -> Box<dyn Iterator<Item = &Node> + '_> {
+        match self {
+            Node::File { name: _, size: _ } => Box::new(iter::empty()),
+            Node::Directory { name: _, children } => Box::new(
+                children.iter().chain(
+                    children
+                        .iter()
+                        .skip(1)
+                        .fold(children[0].walk(), |acc, c| Box::new(acc.chain(c.walk()))),
+                ),
+            ),
+        }
+    }
+}
+
+impl FileSystem {
+    pub fn from_stdin() -> Result<FileSystem, &'static str> {
+        let mut line = String::new();
+        if let Ok(_) = io::stdin().read_line(&mut line) {
+            return Ok(FileSystem {
+                root: FileSystem::parse_dir(&line)?,
+            });
+        }
+        Err("input file is empty")
+    }
+
+    pub fn root(&self) -> &Node {
+        &self.root
+    }
+
+    fn parse_file(line: &str) -> Result<Node, &'static str> {
+        if let Some((size, name)) = line.trim().split_once(' ') {
+            return Ok(Node::File {
+                name: name.into(),
+                size: size.parse().map_err(|_| "failed to parse file")?,
+            });
+        }
+        Err("failed to parse file")
+    }
+
+    fn parse_dir(line: &str) -> Result<Node, &'static str> {
+        if !line.starts_with("$ cd ") {
+            return Err("cannot parse directory");
+        }
+        let name = line[5..].trim();
+        let mut children = vec![];
+        let mut line = String::new();
+        match io::stdin().read_line(&mut line) {
+            Ok(_) if { line == "$ ls\n" } => (),
+            _ => return Err("cannot parse directory"),
+        }
+        loop {
+            line.clear();
+            match io::stdin().read_line(&mut line) {
+                Ok(_) if { line.starts_with("dir ") } => (),
+                Ok(_) if { line.trim().is_empty() || line == "$ cd ..\n" } => break,
+                Ok(_) if { line.starts_with("$ cd ") } => children.push(Self::parse_dir(&line)?),
+                Ok(_) => children.push(Self::parse_file(&line)?),
+                _ => assert!(false),
+            }
+        }
+        Ok(Node::Directory {
+            name: name.into(),
+            children: children,
+        })
+    }
+}
diff --git a/day07/input b/day07/input
new file mode 100644
index 0000000..9a742c8
--- /dev/null
+++ b/day07/input
@@ -0,0 +1,1092 @@
+$ cd /
+$ ls
+dir fts
+dir jnwr
+dir lrvl
+dir nzgprvw
+dir snwqjgj
+16394 tllvcdr.sjl
+195891 zbdp.gqb
+dir zddrb
+$ cd fts
+$ ls
+dir dlqtffw
+dir rbfmmjvd
+254713 wvwhrb.dhh
+$ cd dlqtffw
+$ ls
+73533 nqbvg.fgd
+$ cd ..
+$ cd rbfmmjvd
+$ ls
+290697 zcgrgff.fnf
+$ cd ..
+$ cd ..
+$ cd jnwr
+$ ls
+323577 ghmtnzr
+57588 tdcbdpnr
+dir wbv
+dir zzbvdcf
+$ cd wbv
+$ ls
+dir nmdwbnnr
+253584 slzdbm.ncn
+$ cd nmdwbnnr
+$ ls
+208370 scbcsb.pjg
+$ cd ..
+$ cd ..
+$ cd zzbvdcf
+$ ls
+8052 ssssrhwz
+$ cd ..
+$ cd ..
+$ cd lrvl
+$ ls
+dir bqqltcg
+189288 cwpwh
+90813 jhnddzml.lww
+dir pwc
+dir rjl
+dir rzvqvv
+dir slzdbm
+dir tcbjmq
+140665 zbdp.gqb
+dir zhbpqlnd
+$ cd bqqltcg
+$ ls
+dir dlbjblbf
+dir fdlw
+dir jnwr
+dir slzdbm
+dir zcgrgff
+$ cd dlbjblbf
+$ ls
+11732 rnsrrf.rtv
+$ cd ..
+$ cd fdlw
+$ ls
+dir hlvpfw
+228436 mzsfcvgv.pqw
+$ cd hlvpfw
+$ ls
+dir dhwq
+$ cd dhwq
+$ ls
+127459 cgdpqh.tct
+58310 jnwr.nqt
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd jnwr
+$ ls
+305998 ssssrhwz
+129135 vrt.qdt
+86204 wnvm.bld
+$ cd ..
+$ cd slzdbm
+$ ls
+40915 zbdp.gqb
+120991 zsvffwlt.rbp
+$ cd ..
+$ cd zcgrgff
+$ ls
+94614 jnwr.mqm
+191626 zbdp.gqb
+dir ztrslh
+$ cd ztrslh
+$ ls
+dir bhzn
+201167 dvcjtzvs.rvd
+dir slzdbm
+dir szrth
+dir zcp
+$ cd bhzn
+$ ls
+119164 qbgmrqw
+102090 zbdp.gqb
+$ cd ..
+$ cd slzdbm
+$ ls
+124928 gtdq
+$ cd ..
+$ cd szrth
+$ ls
+dir hpbbsq
+dir vlwlsdjp
+dir zcgrgff
+$ cd hpbbsq
+$ ls
+151717 qsdhff.jsv
+$ cd ..
+$ cd vlwlsdjp
+$ ls
+15049 glpdjtq.mwm
+302526 jnwr.tds
+9550 lhwtbh
+22857 ssssrhwz
+$ cd ..
+$ cd zcgrgff
+$ ls
+73640 mpq.cdn
+dir zcgrgff
+$ cd zcgrgff
+$ ls
+115955 rssmrfbq.trs
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zcp
+$ ls
+dir qdjtmwrr
+dir wpdjttm
+$ cd qdjtmwrr
+$ ls
+138185 jnwr
+$ cd ..
+$ cd wpdjttm
+$ ls
+207755 vvwtghjb
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd pwc
+$ ls
+15911 fqw
+$ cd ..
+$ cd rjl
+$ ls
+119274 ssssrhwz
+$ cd ..
+$ cd rzvqvv
+$ ls
+273935 ssssrhwz
+$ cd ..
+$ cd slzdbm
+$ ls
+dir hlvpfw
+290414 lgzbzjvd.glj
+dir ljpmphn
+316440 slzdbm.tsj
+$ cd hlvpfw
+$ ls
+dir mhvmszgh
+107004 slzdbm
+$ cd mhvmszgh
+$ ls
+dir tftstdp
+$ cd tftstdp
+$ ls
+176794 mpq.cdn
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ljpmphn
+$ ls
+37528 slfdb.bqt
+$ cd ..
+$ cd ..
+$ cd tcbjmq
+$ ls
+96506 lrz.nhb
+$ cd ..
+$ cd zhbpqlnd
+$ ls
+14027 ccswrthv.pfd
+dir clnqtjz
+dir fdsqmnn
+dir fwdt
+dir nljb
+dir npmsdrgp
+57812 slfdb.bqt
+184299 wmlmg
+241025 zcgrgff.wbh
+dir zggqfj
+$ cd clnqtjz
+$ ls
+62391 cbhw.wgr
+309318 jlm.lfq
+dir mzsfcvgv
+dir rrn
+307583 ssssrhwz
+$ cd mzsfcvgv
+$ ls
+1356 hrbh.wpz
+dir vnwqstw
+$ cd vnwqstw
+$ ls
+184434 hnhzdshl.lrl
+150624 wsrnprdb.pjf
+$ cd ..
+$ cd ..
+$ cd rrn
+$ ls
+105792 dzprqqc.rbh
+107482 ffdjdbc
+dir hnr
+dir rdmgtf
+dir rgrwp
+325147 shqr.pdj
+43186 slfdb.bqt
+236667 zcgrgff
+$ cd hnr
+$ ls
+dir gljrlhjm
+250526 mzsfcvgv.nsb
+43164 ssssrhwz
+$ cd gljrlhjm
+$ ls
+dir wjwqrnj
+$ cd wjwqrnj
+$ ls
+142366 gshl.qfc
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rdmgtf
+$ ls
+193562 gdrdnc.vml
+123723 hmqfdht
+dir lzfntb
+dir mjfwsmgd
+208819 nqbgcn.qfq
+dir tqh
+$ cd lzfntb
+$ ls
+dir gwnpsvw
+dir rsgwzhp
+103487 scvllbjh.pnw
+$ cd gwnpsvw
+$ ls
+dir lqnz
+81937 zbdp.gqb
+$ cd lqnz
+$ ls
+27250 zcgrgff
+$ cd ..
+$ cd ..
+$ cd rsgwzhp
+$ ls
+dir hhz
+$ cd hhz
+$ ls
+46435 djvfz
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd mjfwsmgd
+$ ls
+25726 clcvm
+170085 zbdp.gqb
+$ cd ..
+$ cd tqh
+$ ls
+111272 gdq.llg
+3215 hdghs
+dir lpdcdr
+dir vhfr
+$ cd lpdcdr
+$ ls
+203902 hmqfdht
+$ cd ..
+$ cd vhfr
+$ ls
+91584 hmqfdht
+dir stmvj
+$ cd stmvj
+$ ls
+315660 wwpq.ffq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rgrwp
+$ ls
+dir dhwtfld
+187439 hmqfdht
+dir jnwr
+dir npr
+dir sdsppq
+228581 twd.nnc
+42349 wbf.cwb
+194162 zbdp.gqb
+224441 zcgrgff.qpg
+$ cd dhwtfld
+$ ls
+152381 dqdrd
+$ cd ..
+$ cd jnwr
+$ ls
+229758 hmvw.gdz
+92710 mzsfcvgv.cdd
+79954 stjtn.gft
+89831 zbdp.gqb
+$ cd ..
+$ cd npr
+$ ls
+52767 hlvpfw.rqb
+dir nrbjzvgq
+270579 pbsq.msg
+240181 slfdb.bqt
+dir znbwnh
+$ cd nrbjzvgq
+$ ls
+295237 bwqqvn
+229608 dhrjnvtt.lvm
+55391 nlvn
+dir zcgrgff
+$ cd zcgrgff
+$ ls
+124604 hlvpfw.mlw
+$ cd ..
+$ cd ..
+$ cd znbwnh
+$ ls
+228293 zcgrgff
+$ cd ..
+$ cd ..
+$ cd sdsppq
+$ ls
+235741 bcsdzpfj.lvd
+dir jnwr
+dir njtrhrfm
+dir tvq
+dir wshgn
+$ cd jnwr
+$ ls
+273541 brcps
+dir gjt
+dir hlvpfw
+dir nbsdvpnj
+dir zcgrgff
+$ cd gjt
+$ ls
+184707 zbdp.gqb
+$ cd ..
+$ cd hlvpfw
+$ ls
+242810 zcgrgff
+$ cd ..
+$ cd nbsdvpnj
+$ ls
+181797 hlvpfw.gsd
+294284 hmqfdht
+215098 mqbclwwq
+$ cd ..
+$ cd zcgrgff
+$ ls
+188814 hmqfdht
+$ cd ..
+$ cd ..
+$ cd njtrhrfm
+$ ls
+dir dqpjdztt
+$ cd dqpjdztt
+$ ls
+178036 vwg
+$ cd ..
+$ cd ..
+$ cd tvq
+$ ls
+233085 rmq.zgq
+215613 slzdbm.wvf
+$ cd ..
+$ cd wshgn
+$ ls
+209007 jnwr.hsr
+dir ntrlll
+$ cd ntrlll
+$ ls
+245558 jnwr.tbr
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd fdsqmnn
+$ ls
+dir dfl
+dir hqffnmq
+268076 zcgrgff.cfm
+dir ztc
+$ cd dfl
+$ ls
+5553 bbvqpgf
+128390 lqtvvc.tdj
+190189 vnmfcdws
+$ cd ..
+$ cd hqffnmq
+$ ls
+28438 ssssrhwz
+$ cd ..
+$ cd ztc
+$ ls
+247470 slfdb.bqt
+$ cd ..
+$ cd ..
+$ cd fwdt
+$ ls
+60342 bdwbzpzz
+dir cdcc
+dir jldlzttm
+261042 ssssrhwz
+dir sws
+293090 zbdp.gqb
+93624 zcgrgff.vgh
+$ cd cdcc
+$ ls
+dir cwpfczr
+dir lsrgfml
+$ cd cwpfczr
+$ ls
+303853 wzz.chs
+$ cd ..
+$ cd lsrgfml
+$ ls
+63205 hmqfdht
+$ cd ..
+$ cd ..
+$ cd jldlzttm
+$ ls
+184715 brclwptp
+309967 gdbfh.vhn
+5460 hlvpfw.fwb
+46159 jnwr.ggw
+173896 zbdp.gqb
+$ cd ..
+$ cd sws
+$ ls
+dir hlvpfw
+75133 nqrp.jdg
+$ cd hlvpfw
+$ ls
+71403 cvdd.whl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nljb
+$ ls
+105380 lrhmdl
+$ cd ..
+$ cd npmsdrgp
+$ ls
+176062 bhm.gfd
+dir dgdl
+24535 fdfmntpt.qvp
+dir jnwr
+279503 ssssrhwz
+4671 zbdp.gqb
+$ cd dgdl
+$ ls
+4624 qqcp.rcg
+$ cd ..
+$ cd jnwr
+$ ls
+dir cvw
+122648 hmqfdht
+26565 jnwr.fst
+271544 jnwr.tqb
+170968 mpq.cdn
+dir ncqflwrb
+103826 qgzlff.frl
+dir wclwg
+dir wtcfswt
+$ cd cvw
+$ ls
+58583 pjthqdbr.zzh
+398 ssssrhwz
+$ cd ..
+$ cd ncqflwrb
+$ ls
+105747 wwstfng.cdl
+$ cd ..
+$ cd wclwg
+$ ls
+75020 wbq
+$ cd ..
+$ cd wtcfswt
+$ ls
+182813 dnln
+255923 hmqfdht
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zggqfj
+$ ls
+dir gpnfpv
+dir gzfsnbv
+186684 jnwr
+dir msrz
+$ cd gpnfpv
+$ ls
+dir hlvpfw
+$ cd hlvpfw
+$ ls
+186814 bgqpn
+41444 mzsfcvgv.qpp
+292879 zcgrgff
+$ cd ..
+$ cd ..
+$ cd gzfsnbv
+$ ls
+321796 jnwr.ghb
+dir sdgwjtf
+$ cd sdgwjtf
+$ ls
+127216 mzsfcvgv.qlv
+$ cd ..
+$ cd ..
+$ cd msrz
+$ ls
+dir fzl
+32371 jqtgpzw.thg
+271389 slfdb.bqt
+270845 tchtnp.rsw
+146371 zmwbmj
+$ cd fzl
+$ ls
+140610 ssssrhwz
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nzgprvw
+$ ls
+dir hgfdbf
+218138 mpq.cdn
+73419 slfdb.bqt
+dir vfztvnjm
+269866 wldptfv.bbb
+dir zgdsgh
+$ cd hgfdbf
+$ ls
+163792 ssssrhwz
+262305 zcgrgff
+$ cd ..
+$ cd vfztvnjm
+$ ls
+139863 hlvpfw
+138410 hmqfdht
+$ cd ..
+$ cd zgdsgh
+$ ls
+194820 dhp.tgt
+dir hlvpfw
+dir sdllphqd
+dir zcgrgff
+$ cd hlvpfw
+$ ls
+44509 hmqfdht
+$ cd ..
+$ cd sdllphqd
+$ ls
+47133 mpq.cdn
+$ cd ..
+$ cd zcgrgff
+$ ls
+186613 jrrpljrc
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd snwqjgj
+$ ls
+dir slzdbm
+dir zcgrgff
+dir zldscsc
+$ cd slzdbm
+$ ls
+21422 dplgjzvs.nrn
+175310 zcgrgff.dfq
+$ cd ..
+$ cd zcgrgff
+$ ls
+dir rrfhvjf
+275455 vwnvj.nhb
+dir zcgrgff
+$ cd rrfhvjf
+$ ls
+69149 mqmwv.jmr
+$ cd ..
+$ cd zcgrgff
+$ ls
+dir zcgrgff
+$ cd zcgrgff
+$ ls
+183398 hmqfdht
+93968 sdhmwd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zldscsc
+$ ls
+dir fmzvccvg
+299187 mpq.cdn
+324288 mzsfcvgv.srz
+dir prdfldrf
+dir sgpdqw
+289150 ssssrhwz
+3330 vwwj
+133537 wbb.fdl
+dir wjdpws
+$ cd fmzvccvg
+$ ls
+dir brrlg
+dir crm
+dir mzsfcvgv
+$ cd brrlg
+$ ls
+17776 jnwr.qqz
+$ cd ..
+$ cd crm
+$ ls
+220545 mltrj
+177044 mzsfcvgv.thj
+$ cd ..
+$ cd mzsfcvgv
+$ ls
+51223 pdnbml.qpg
+$ cd ..
+$ cd ..
+$ cd prdfldrf
+$ ls
+213872 ftw
+$ cd ..
+$ cd sgpdqw
+$ ls
+205684 whrfvw.dph
+$ cd ..
+$ cd wjdpws
+$ ls
+dir hlvpfw
+$ cd hlvpfw
+$ ls
+324522 zbdp.gqb
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zddrb
+$ ls
+238213 dhrdjfzl.npj
+28938 hlvpfw
+313900 hlvpfw.bwd
+dir pgbgpn
+132967 rrhsr
+dir slzdbm
+142210 wlvpwjjz
+dir zdhcp
+$ cd pgbgpn
+$ ls
+dir jpmvrvt
+154268 mpq.cdn
+dir mzsfcvgv
+dir vvmwgngv
+$ cd jpmvrvt
+$ ls
+150157 ghcvqm
+$ cd ..
+$ cd mzsfcvgv
+$ ls
+93810 mjglpwbc.tvt
+dir slzdbm
+$ cd slzdbm
+$ ls
+dir jnwr
+174522 slzdbm.ncl
+$ cd jnwr
+$ ls
+183686 rpwjvc
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd vvmwgngv
+$ ls
+dir bqc
+dir mzsfcvgv
+dir qgj
+dir wfjzls
+$ cd bqc
+$ ls
+191442 bqsn
+dir lmnvtg
+278861 mpq.cdn
+191779 mthgd.mjp
+dir mzsfcvgv
+dir twzq
+$ cd lmnvtg
+$ ls
+dir dzdd
+7920 hmqfdht
+dir rnlctfm
+dir slzdbm
+213184 zcgrgff.vln
+$ cd dzdd
+$ ls
+dir jnwr
+$ cd jnwr
+$ ls
+71772 hlvpfw
+$ cd ..
+$ cd ..
+$ cd rnlctfm
+$ ls
+282289 jvnmblr.mdc
+24454 ssssrhwz
+$ cd ..
+$ cd slzdbm
+$ ls
+316131 mzsfcvgv.czz
+$ cd ..
+$ cd ..
+$ cd mzsfcvgv
+$ ls
+dir nsvn
+dir plj
+dir tvmv
+$ cd nsvn
+$ ls
+dir bcmd
+dir jcjsp
+dir jnwr
+$ cd bcmd
+$ ls
+206778 cpljbvm.vws
+86096 lfgjnzhw.rtm
+$ cd ..
+$ cd jcjsp
+$ ls
+188389 zbdp.gqb
+$ cd ..
+$ cd jnwr
+$ ls
+293633 jhh.wtj
+$ cd ..
+$ cd ..
+$ cd plj
+$ ls
+323119 qgs
+221100 ssssrhwz
+264549 zbdp.gqb
+$ cd ..
+$ cd tvmv
+$ ls
+198197 mpq.cdn
+$ cd ..
+$ cd ..
+$ cd twzq
+$ ls
+dir hwgndwpj
+$ cd hwgndwpj
+$ ls
+dir srdzqqf
+$ cd srdzqqf
+$ ls
+101738 slzdbm
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd mzsfcvgv
+$ ls
+dir hlvpfw
+dir vbdw
+$ cd hlvpfw
+$ ls
+270309 wncrt
+$ cd ..
+$ cd vbdw
+$ ls
+dir csw
+$ cd csw
+$ ls
+231750 dcjr.jgb
+297504 mpq.cdn
+215564 plm.rtl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd qgj
+$ ls
+192181 hmqfdht
+dir lmp
+250495 mpq.cdn
+dir slzdbm
+253262 ssssrhwz
+dir tzth
+$ cd lmp
+$ ls
+dir jnwr
+$ cd jnwr
+$ ls
+284951 zcgrgff.slq
+$ cd ..
+$ cd ..
+$ cd slzdbm
+$ ls
+266715 hzbq.plc
+dir jnwr
+11379 mzsfcvgv.rbw
+dir slzdbm
+$ cd jnwr
+$ ls
+108636 mpq.cdn
+324035 zzvmlrj.rrl
+$ cd ..
+$ cd slzdbm
+$ ls
+68393 zbdp.gqb
+$ cd ..
+$ cd ..
+$ cd tzth
+$ ls
+12884 hlvpfw.gwl
+146470 jnwr
+$ cd ..
+$ cd ..
+$ cd wfjzls
+$ ls
+191088 hlvpfw.prw
+64712 mpq.cdn
+103828 pjhg.qmc
+dir qvmdt
+$ cd qvmdt
+$ ls
+244001 ssssrhwz
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd slzdbm
+$ ls
+dir hsvbbbp
+dir jdtrdgqs
+dir lrldsqcr
+194137 mzsfcvgv.hnv
+dir nzcbqzdz
+$ cd hsvbbbp
+$ ls
+104752 rcfpnh.vlr
+185473 slzdbm.dbr
+dir vpwf
+dir zhngz
+$ cd vpwf
+$ ls
+266988 frhvp.ltf
+82931 mpq.cdn
+$ cd ..
+$ cd zhngz
+$ ls
+181282 drtfhrhp
+$ cd ..
+$ cd ..
+$ cd jdtrdgqs
+$ ls
+37106 hdjl.rrr
+$ cd ..
+$ cd lrldsqcr
+$ ls
+dir brwcprn
+dir hlvpfw
+dir jnwr
+dir slzdbm
+dir wrmr
+dir zjrdgf
+dir zrpqf
+$ cd brwcprn
+$ ls
+dir bmjwts
+$ cd bmjwts
+$ ls
+157148 jwbd
+251396 qtgc
+$ cd ..
+$ cd ..
+$ cd hlvpfw
+$ ls
+121723 zbdp.gqb
+$ cd ..
+$ cd jnwr
+$ ls
+240747 gfrrtdh
+$ cd ..
+$ cd slzdbm
+$ ls
+176832 jnwr
+36125 ltwmzw.fdl
+132059 plqmwhr.hhv
+85540 slzdbm.wzm
+23459 zhbwh.cds
+$ cd ..
+$ cd wrmr
+$ ls
+90357 zbdp.gqb
+$ cd ..
+$ cd zjrdgf
+$ ls
+301679 qbmt.vhh
+12942 slfdb.bqt
+$ cd ..
+$ cd zrpqf
+$ ls
+241851 pnsdlbs.brw
+$ cd ..
+$ cd ..
+$ cd nzcbqzdz
+$ ls
+182963 qgg.zsc
+dir qwjgb
+301344 slfdb.bqt
+299029 zbdp.gqb
+$ cd qwjgb
+$ ls
+223978 rprrjp.hfd
+164106 wlq.rcq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zdhcp
+$ ls
+dir hbggp
+dir mzsfcvgv
+dir zdsvth
+$ cd hbggp
+$ ls
+302339 qcmfdhvm
+112806 rpb.vfl
+$ cd ..
+$ cd mzsfcvgv
+$ ls
+dir gpz
+dir slzdbm
+dir zvjv
+$ cd gpz
+$ ls
+290264 fdl
+158548 slfdb.bqt
+$ cd ..
+$ cd slzdbm
+$ ls
+dir hlvpfw
+dir mzsfcvgv
+dir zdcthssc
+$ cd hlvpfw
+$ ls
+49287 zbdp.gqb
+$ cd ..
+$ cd mzsfcvgv
+$ ls
+dir gnmtggs
+103244 jnwr.gtn
+263736 slfdb.bqt
+$ cd gnmtggs
+$ ls
+31665 qhthp.lfh
+$ cd ..
+$ cd ..
+$ cd zdcthssc
+$ ls
+64408 cgbnzc.cgn
+$ cd ..
+$ cd ..
+$ cd zvjv
+$ ls
+6088 gnpsb.dml
+145405 llp.cbm
+dir mgcg
+dir nwl
+dir rqznjmt
+128194 zbdp.gqb
+$ cd mgcg
+$ ls
+dir ngwvm
+dir slzdbm
+dir smd
+dir smr
+dir zcgrgff
+$ cd ngwvm
+$ ls
+49186 hmqfdht
+$ cd ..
+$ cd slzdbm
+$ ls
+44434 rdcb
+$ cd ..
+$ cd smd
+$ ls
+dir fjd
+dir rscdvnwt
+dir wbhp
+318166 zbdp.gqb
+$ cd fjd
+$ ls
+14084 hlvpfw.ghn
+$ cd ..
+$ cd rscdvnwt
+$ ls
+6432 fzwpmjm.ntl
+$ cd ..
+$ cd wbhp
+$ ls
+dir czv
+217474 dnq.cpq
+36009 jnwr.zdv
+32123 mpq.cdn
+27607 mrm.sgs
+107593 zbdp.gqb
+$ cd czv
+$ ls
+60750 zcgrgff.mnr
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd smr
+$ ls
+47204 zcgrgff.vsl
+$ cd ..
+$ cd zcgrgff
+$ ls
+317050 hjtfb
+110272 jrbcbvjw
+290867 ltfj.dvl
+dir mzsfcvgv
+130694 wnc.rnr
+206448 zbdp.gqb
+$ cd mzsfcvgv
+$ ls
+dir jnwr
+$ cd jnwr
+$ ls
+20405 bjpvssjt
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nwl
+$ ls
+254439 dlv
+193910 hlvpfw
+13603 hnsdntn.trz
+2990 mpq.cdn
+$ cd ..
+$ cd rqznjmt
+$ ls
+250114 hlvpfw
+189732 mzsfcvgv.vqv
+144688 zcgrgff
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd zdsvth
+$ ls
+150609 jnwr.rtr
+173402 nftm.nwd
+dir njhjrgmf
+$ cd njhjrgmf
+$ ls
+295762 nchztlh.lcs
+
diff --git a/day07/part1.rs b/day07/part1.rs
new file mode 100644
index 0000000..817e8a7
--- /dev/null
+++ b/day07/part1.rs
@@ -0,0 +1,39 @@
+// Copyright 2022 Christian Ulrich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+// usage: ./part1 < input
+
+pub mod common;
+
+use common::{FileSystem, Node};
+
+fn main() -> Result<(), &'static str> {
+    let fs = FileSystem::from_stdin()?;
+    let mut result = 0;
+    for node in fs.root().walk() {
+        if let Node::Directory {
+            name: _,
+            children: _,
+        } = node
+        {
+            let size = node.size();
+            if size <= 100000 {
+                result += size;
+            }
+        }
+    }
+    println!("{result}");
+    Ok(())
+}
diff --git a/day07/testinput b/day07/testinput
new file mode 100644
index 0000000..09a921e
--- /dev/null
+++ b/day07/testinput
@@ -0,0 +1,23 @@
+$ 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