a, b, c = map(int, input().split())
if a == b == c:
    print(a)
elif a == b:
    print(c)
elif a == c:
    print(b)
elif c == b:
    print(a)
elif a != b and b != c and a != c:
    print(list({a, b, c}^{0, 1, 2, 3})[0])