def bin_length(N):
    ret = 0
    while N >= pow(2, ret):
        ret += 1
    return ret - 1

A,B = map(int,input().split())
if A > B:
    A,B = B,A
a = bin_length(A)
b = bin_length(B)
if a < b:
    print(A)
else:
    print(pow(2, a) - 1)