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

a = len(bin(A)) - 2
b = len(bin(B)) - 2
import sys
if a == b:
    ans = (1 << (a - 1)) - 1
    print(ans)
else:
    if b < a:
        a,b = b,a
        A,B = B,A
    print(A)