#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using vvb = vector<vb>;
#define LLINF 9223372036854775807
#define MOD ll(998244353)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cerr<<#x<<": "<<x<<endl


int main(){
    ll a, b;
    cin >> a >> b;

    ll c = min(a, b);
    if(a == b){c--;}
    ll ans = 0;
    ll t = 1;
    for(int i = 0; i < 1000; i++){
        t *= 2;
        if(t-1 <= c){ans = t-1;}
        else{
            cout << ans << endl;
            break;
        }
        
    }
    return 0;
}