a, b, c = [int(x) for x in input().split()]
if a == b == c:
    print(a)
elif a == b:
    print(c)
elif b == c:
    print(a)
elif c == a:
    print(b)
else:
    print(list(set([0, 1, 2, 3]) - set([a, b, c]))[0])