from collections import Counter, defaultdict, deque
import itertools
import re
import math
from functools import reduce
import operator
import bisect
from heapq import *
import functools
mod=998244353

import sys
input=sys.stdin.readline
a,b=map(int,input().split())
if a.bit_length() != b.bit_length():
    print(min(a,b))
else:
    print((1 << (a.bit_length() - 1)) - 1)