import sys
sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LC(): return list(input())
def IC(): return [int(c) for c in input()]
def MI(): return map(int, sys.stdin.readline().split())
INF = float('inf')
MOD = 10**9 + 7
def solve():
    A,B = MI()
    print((A|B) - (A&B))
    return
solve()