#! /usr/bin/env ruby

if ARGV.length != 1
        abort("Incorrect arguments - needs input file")
elsif not File.exist? (ARGV[0])
	abort("File #{ARGV[0]} did not exist")
end

file = ARGV[0]

histories = File.open(file, "r").each_line(chomp: true).map {|line| line.split(" ").map(&:to_i)}

def diff_array(arr)
	arr.each_cons(2)
	
end

predictions = histories.map do |history|
	vals = history
	layers = [history]
	while not vals.all? {|v| v == 0}
		vals = vals.each_cons(2).map {|a,b| b - a}
		layers << vals
	end
	layers.reverse!.each_cons(2).map {|diffs, vals| vals.insert(0, vals[0] - diffs[0])}
	layers[-1][0]
end

puts predictions.sum
# Rest of algorithm here