#!/usr/bin/python3

# https://www.hackerrank.com/challenges/maximizing-xor

import sys

def max_xor(L,R):
	res = 1
	n = L ^ R
	while n > 0:
		n >>=1
		res <<= 1
	return res - 1

def main():
	L = int(sys.stdin.readline())
	R = int(sys.stdin.readline())
	print(max_xor(L,R))

if __name__ == '__main__':
	main()