A, B = map(int, input().split())
A, B = min(A, B), max(A, B)

for i in range(40):
    if (A>>i)&1:
        a = i
    
for i in range(40):
    if (B>>i)&1:
        b = i

if a<b:
    print(A)
else:
    print((1<<a)-1)