import sys
L = [list(map(int,l.split(' '))) for l in sys.stdin.read().splitlines()]

def extrapolate(L):
    if all(not a for a in L):
        return L+[0]
    M = [b-a for a,b in zip(L,L[1:])]
    return L+[L[-1]+extrapolate(M)[-1]]


for l in L:
    print(extrapolate(l)[-1])
#print(sum(extrapolate(l)[-1] for l in L))