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, b = mi()
ans = 0
for i in range(0, 33):
    if a >= 2 ** i - 1 and b >= 2 ** i - 1:
        ans = 2 ** i - 1
print(ans)