#!/usr/bin/env python3
# -*- coding: utf-8 -*-
input_file = open("input", "r")
data = [[int(i) for i in line.strip().split()]for line in input_file]
input_file.close()


def find_diff(val_list):
    if val_list.count(0) == len(val_list):
        return 0
    return val_list[0]-find_diff([(val_list[i+1]-val_list[i]) for i in range(len(val_list)-1)])


print("Lösung:", sum([find_diff(d) for d in data]))