diff --git a/day7.erl b/day7.erl
new file mode 100644
index 0000000..cb8ce2c
--- /dev/null
+++ b/day7.erl
@@ -0,0 +1,32 @@
+-module(day7).
+
+-export([solve/1]).
+
+solve(InputData) ->
+	Input = binary:split(InputData, <<"\n">>, [trim_all, global]),
+	#{sizes := Sizes} = lists:foldl(fun execute/2, #{cwd => [], sizes => #{}}, Input),
+	{maps:fold(fun adder/3, 0, Sizes), none}.
+
+adder(_Path, Size, Total) when Size > 100000 -> Total;
+adder(_Path, Size, Total) -> Size + Total.
+
+execute(<<"$ cd /">>, State) -> State#{cwd := []};
+execute(<<"$ cd ..">>, #{cwd := [_Cwd | Parent]} = State) -> State#{cwd := Parent};
+execute(<<"$ cd ", Dir/binary>>, #{cwd := Cwd} = State) -> State#{cwd := [Dir | Cwd]};
+execute(<<"$ ls">>, State) -> State;
+execute(<<"dir ", Dir/binary>>, #{cwd := Cwd} = State) -> State#{[Dir | Cwd] => 0};
+execute(FileCommand ,#{cwd := Cwd, sizes := Sizes} = State) ->
+	{Filename, Size} = parse_file_command(FileCommand),
+	State#{sizes := add_sizes(Cwd, Size, Sizes)}.
+
+parse_file_command(Command) -> parse_file_command(Command, 0).
+
+parse_file_command(<<$\s, Name/binary>>, Size) -> {Name, Size};
+parse_file_command(<<Digit, Rest/binary>>, Size) -> parse_file_command(Rest, (Size*10) + (Digit - $0)).
+
+add_sizes(Path, Size, Sizes) ->
+	NewSizes = maps:update_with(Path, fun(OldSize) -> OldSize + Size end, Size, Sizes),
+	case Path of
+		[] -> NewSizes;
+		[_Head| Parent] -> add_sizes(Parent, Size, NewSizes)
+	end.