# Day 13
```elixir
Mix.install([{:kino, "~> 0.5.0"}])
```
## Input
```elixir
input = """
[1,1,3,1,1]
[1,1,5,1,1]
[[1],[2,3,4]]
[[1],4]
[9]
[[8,7,6]]
[[4,4],4,4]
[[4,4],4,4,4]
[7,7,7,7]
[7,7,7]
[]
[3]
[[[]]]
[[]]
[1,[2,[3,[4,[5,6,7]]]],8,9]
[1,[2,[3,[4,[5,6,0]]]],8,9]
"""
```
```elixir
input = Kino.Input.textarea("paste input here:")
```
<!-- livebook:{"reevaluate_automatically":true} -->
```elixir
input =
input
|> Kino.Input.read()
|> String.split()
|> Enum.map(fn list -> list |> Code.eval_string() |> elem(0) end)
```
## Common
```elixir
defmodule Packet do
def compare([], []), do: :eq
def compare([], _), do: :lt
def compare(_, []), do: :gt
def compare([l | ls], [r | rs]) when is_integer(l) and is_integer(r) do
cond do
l < r -> :lt
l > r -> :gt
l == r -> compare(ls, rs)
end
end
def compare([l | ls], [r | rs]) when is_list(l) and is_list(r) do
case compare(l, r) do
:lt -> :lt
:gt -> :gt
:eq -> compare(ls, rs)
end
end
def compare([l | ls], right) when is_integer(l), do: compare([[l] | ls], right)
def compare(left, [r | rs]) when is_integer(r), do: compare(left, [[r] | rs])
end
```
## Part 1
```elixir
for {[left, right], i} <- input |> Enum.chunk_every(2) |> Enum.with_index(1),
:lt == Packet.compare(left, right) do
i
end
|> Enum.sum()
```
## Part 2
```elixir
sorted =
input
|> Enum.concat([[[2]], [[6]]])
|> Enum.sort(Packet)
start_index = 1 + Enum.find_index(sorted, &(&1 == [[2]]))
end_index = 1 + Enum.find_index(sorted, &(&1 == [[6]]))
start_index * end_index
```
