from operator import itemgetter
from itertools import *
from bisect import *
from collections import *
from heapq import *
import sys

# input=sys.stdin.buffer.readline
input=sys.stdin.readline

sys.setrecursionlimit(10**6)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(input())
def MI(): return map(int, input().split())
def MI1(): return map(int1, input().split())
def LI(): return list(map(int, input().split()))
def LI1(): return list(map(int1, input().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def SI(): return input()[:-1]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
dij = [(1, 0), (0, 1), (-1, 0), (0, -1)]

a,c=MI()
print(a^c)