from collections import Counter,defaultdict,deque
from heapq import heappop,heappush,heapify
from bisect import bisect_left,bisect_right
import sys,math,itertools,pprint,fractions
sys.setrecursionlimit(10**8)
mod = 10**9+7
INF = float('inf')
def inp(): return int(sys.stdin.readline())
def inpl(): return list(map(int, sys.stdin.readline().split()))
def inpl_1(): return list(map(lambda x:int(x)-1, sys.stdin.readline().split()))
def err(x): print(x); exit()

a,b = inpl()
if a<b:
    a,b = b,a
ln = len(bin(a)[2:])
print(min(pow(2,ln-1)-1, b))