diff --git a/lib/2023_day5.ex b/lib/2023_day5.ex
new file mode 100644
index 0000000..38f4cb1
--- /dev/null
+++ b/lib/2023_day5.ex
@@ -0,0 +1,72 @@
+defmodule Mix.Tasks.Day5 do
+  use Mix.Task
+
+  def run(_) do
+    IO.stream() |> parse() |> part1() |> IO.puts()
+  end
+
+  def split_int_list(s, sep) do
+    s |> String.split(sep) |> Enum.map(fn n -> Integer.parse(n) |> elem(0) end)
+  end
+
+  def parse_line("seeds: " <> seeds) do
+    {:seeds, seeds |> split_int_list(" ")}
+  end
+
+  def parse_line(line) when line != "" do
+    make_range = fn line ->
+      [dest_start, source_start, len] = line |> split_int_list(" ")
+       {:range, {RangeUtil.from_start(dest_start, len), RangeUtil.from_start(source_start, len)}}
+    end
+    cap = Regex.run(~r/(\w+)-to-(\w+) map:/, line)
+    case cap do
+     [_, source, dest] -> {:map_key, { source |> String.to_atom(), dest |> String.to_atom() } }
+     nil -> make_range.(line)
+   end
+  end
+
+  def parse(input) do
+    for line <- input,
+      line = line |> String.trim(),
+      line != "",
+      reduce: %{} do
+      acc ->
+        {type, data} = parse_line(line)
+        case type do
+          :seeds -> acc |> Map.put(type, data)
+          :map_key -> { source, dest } = data
+            acc 
+              |> Map.update(:maps, %{source => {dest, []}}, fn maps -> maps |> Map.put(source, {dest, []}) end)
+              |> Map.put(:last_map_key, source)
+          :range -> %{last_map_key: last_map_key} = acc
+            acc |> Map.update!(
+              :maps,
+              fn maps -> maps 
+                |> Map.update!(last_map_key, fn {dest, ranges} ->
+                  {dest, [data | ranges]}
+                end)
+              end)
+        end
+    end
+  end
+  def get_location(:location, n, _) do
+    n
+  end
+  def get_location(source, n, maps) do
+    {dest, ranges} = maps |> Map.get(source)
+    transpose = case ranges |> Enum.find(fn {_, source} ->
+      n in source
+    end) do
+      {dest_range, source_range} ->RangeUtil.transpose(n, source_range, dest_range)
+      nil -> n
+    end
+    IO.puts({dest, transpose} |> inspect())
+    get_location(dest, transpose, maps)
+  end
+
+  def part1(state) do
+    for seed <- state.seeds do
+      get_location(:seed, seed, state.maps)
+    end |> Enum.min()
+  end
+end
diff --git a/test/2023_day5_test.exs b/test/2023_day5_test.exs
new file mode 100644
index 0000000..b3ddb15
--- /dev/null
+++ b/test/2023_day5_test.exs
@@ -0,0 +1,78 @@
+defmodule Day5Tests do
+  use ExUnit.Case
+
+  test "parse seeds correctly" do
+    assert Mix.Tasks.Day5.parse_line("seeds: 79 14 55 13") == {:seeds, [79, 14, 55, 13]}
+  end
+  
+  test "parse map line def" do
+    assert Mix.Tasks.Day5.parse_line("seed-to-soil map:") == {:map_key, { :seed, :soil }}
+  end
+
+  test "parse map line fails" do
+    assert Mix.Tasks.Day5.parse_line("50 98 2") == {:range, {50..51, 98..99}}
+  end
+
+  test "range util does not lie" do
+    assert (RangeUtil.from_start(120, 300) |> Enum.count()) === 300 
+  end
+
+  test "range util transpose does not lie" do
+    assert RangeUtil.transpose(98, 98..99, 50..51) === 50
+  end
+
+  test "parse works" do
+    ex = ~s"seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48"
+    assert Mix.Tasks.Day5.parse(ex |> String.split("\n")) == %{
+      :seeds => [79, 14, 55, 13], 
+      :maps => %{:seed => {:soil, [{52..99, 50..97}, {50..51, 98..99}]}},
+      :last_map_key => :seed
+    }
+  end
+
+  test "parse doesn't crash with whole input" do
+    ex = ~s"seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+
+temperature-to-humidity map:
+
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4
+"
+  assert ex |> String.split("\n") |> Mix.Tasks.Day5.parse() |> Mix.Tasks.Day5.part1() == 35
+  end
+end