#!/usr/bin/env python3
from math import comb

lines = (x.strip() for x in open("input.txt"))
result = 0

for line in lines:
    numbers = [int(x) for x in line.split(" ")]
    result += sum(((idx+len(numbers))%2*2-1) * comb(len(numbers), idx) * val for idx, val in enumerate(numbers))

print(result)