import sys
import pypyjit
import itertools
import heapq
import math
from collections import deque, defaultdict
import bisect

input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)
pypyjit.set_param('max_unroll_recursion=-1')


A, B = map(int, input().split())
acc = 1
for i in range(30 + 1):
    n = 1 if A & (1 << i) else 0
    m = 1 if B & (1 << i) else 0

    if n == 1 and m == 0:
        acc = 0
        break
    if n == 0 and m == 1:
        acc <<= 1
print(acc >> 1 if acc > 1 else acc)