import sys, math
sys.setrecursionlimit(1000000)
INF = 1 << 100
#mod = 1000000007
mod = 998244353
input = lambda: sys.stdin.readline().rstrip()
li = lambda: list(map(int, input().split()))

A, B = li()
if B > A:
    A, B = B, A
N = len(bin(A)) - 2
M = len(bin(B)) - 2


if A == 0 or B == 0:
    print(0)
elif N == M:
    A ^= (1 << (N-1))
    print((1 << (N - 1)) - 1)
elif N != M:
    print(B)