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# Day 25
```elixir
Mix.install([{:kino, "~> 0.5.0"}])
```
## Section
```elixir
input = Kino.Input.textarea("paste input here:")
```
```elixir
input = Kino.Input.read(input)
```
```elixir
defmodule SNAFU do
def to_integer(snafu) do
snafu
|> String.to_charlist()
|> Enum.reverse()
|> Enum.with_index(fn chr, digit ->
5 ** digit *
case chr do
?2 -> 2
?1 -> 1
?0 -> 0
?- -> -1
?= -> -2
end
end)
|> Enum.sum()
end
def to_snafu(n, last_power \\ nil)
def to_snafu(0, last_power), do: List.duplicate(?0, last_power)
def to_snafu(n, last_power) do
{pow, max_subtraction} =
Stream.iterate({1, 0}, fn {pow, _} ->
{pow + 1, div(5 ** pow, 2)}
end)
|> Stream.take_while(fn {_, prev} -> prev < abs(n) end)
|> Enum.at(-1)
|> IO.inspect()
pow = pow - 1
digit = div(n + div(n, abs(n)) * max_subtraction, 5 ** pow)
chr_digit =
case digit do
2 -> ?2
1 -> ?1
0 -> ?0
-1 -> ?-
-2 -> ?=
end
IO.inspect([digit])
IO.inspect(n - digit * 5 ** pow)
# IO.inspect({last_power, pow})
if last_power do
List.duplicate(?0, last_power - pow - 1)
else
[]
end ++
[chr_digit | to_snafu(n - digit * 5 ** pow, pow)]
end
end
SNAFU.to_integer("2=-1=0")
SNAFU.to_snafu(4890)
```
```elixir
input
|> String.split()
|> Enum.map(&SNAFU.to_integer/1)
|> Enum.sum()
|> SNAFU.to_snafu()
```
```elixir
SNAFU.to_integer("20-1-0=-2=-2220=0011")
```
See source 
