#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll N_MAX = 2e5;

ll digit(ll x){
    ll res = 0;
    while(x){
        res++;
        x/=2;
    }

    return res;
}

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

    if(digit(a) != digit(b)) cout << min(a, b) << endl;
    else{
        cout << ((1<<(digit(a)-1))-1) << endl;
    }
}