/* -*- coding: utf-8 -*-
 *
 * 1957.cc:  No.1957 Xor Min - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

inline int msb(int n) {
  int b = 1;
  while ((b << 1) <= n) b <<= 1;
  return b;
}

/* subroutines */

/* main */

int main() {
  int a, b;
  scanf("%d%d", &a, &b);

  if (a > b) swap(a, b);

  int amsb = msb(a), bmsb = msb(b);

  printf("%d\n", (amsb == bmsb) ? amsb - 1 : a);
  return 0;
}