#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;
 
#include<bits/stdc++.h>
using namespace std;
 
int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  ll a,b;
  cin>>a>>b;
  if(a>b) swap(a,b);
  ll c=a,d=b;
  int t0=0,t1=0;
  while(c>0){
    t0++;
    c/=2;
  }
  while(d>0){
    t1++;
    d/=2;
  }
  if(t0!=t1) cout<<a<<endl;
  else cout<<(1<<(t0-1))-1<<endl;

  return 0;
}