#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
ll inf=10010010010010010;
ll mod=1000000007;
int main(){
    ll a,b;
    cin >> a >> b ;
    ll x=1;
    while (x<a&&x<b)
    {
        x*=2;
    }
    if (x==a||x==b)
    {
        if (a==b)
        {
            cout << x-1 << endl;
        }else if (max(a,b)>=x*2)
        {
            cout << x << endl;
        }else{
            cout << x-1 << endl;
        }
    }else{
        if (x-1==min(a,b))
        {
            cout << x-1 << endl;
            return 0;
        }
        x/=2;
        x-=1;
        cout << x << endl;
    }
    
}