import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
INF = 2 ** 63 - 1
mod = 998244353


a = li()

a.sort()

if a[0] == a[1]:
    print(a[2])
elif a[1] == a[2]:
    print(a[0])
else:
    print(6 - sum(a))