#!/bin/env ruby
require 'pry'
numbers = File.read('./input').split(',')
numbers.map!(&:to_i)

runs = 30000000

runs.times do |i|
    next if i < numbers.size
    num = numbers[-1]
    prev_turn = numbers[..-2].reverse.find_index(num)
    if prev_turn == nil
        numbers.push(0)
    else
        new_num = (i - 1) - (numbers.size - 2 - prev_turn)
        numbers.push(new_num)
    end
end

puts numbers[-1]