a, b = map(int, input().split())

ac, bc = a, b
a_d, b_d = 0, 0
A = [0 for _ in range(31)]
B = [0 for _ in range(31)]
for i in range(31):
    A[i] = ac % 2
    if A[i] == 1:
        a_d = i
    ac //= 2
    B[i] = bc % 2
    if B[i] == 1:
        b_d = i
    bc //= 2

if a_d > b_d:
    print(b)
elif a_d < b_d:
    print(a)
else:
    print(2**a_d - 1)