a,b = map(int,input().split())
if b > a:
    a,b = b,a

for i in range(30):
    if a >> i & 1:
        base = 1<<i
        
ans = 0
for i in range(30)[::-1]:
    x = 1<<i
    if x < base and x <= b:
        ans += x
print(ans)