#include <bits/stdc++.h>
//#include <atcoder/all>
//using namespace atcoder;
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
using pqr = priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>>;

bool chmax(ll& p, ll q) {
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

bool chmin(ll& p, ll q) {
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}
ll gcd(ll(a), ll(b)) {
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}


void warshall_floyd(int n, vvll& d) {
    for (int k = 0; k < n; k++) {       // 経由する頂点
        for (int i = 0; i < n; i++) {    // 始点
            for (int j = 0; j < n; j++) {  // 終点
                d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
            }
        }
    }
}




int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll N,M;
    cin>>N>>M;
    if(N>M)swap(N,M);
    ll a=1,b=1;
    ll P=N;
    while(P>0){
        P/=2;
        a*=2;
    }
    P=M;
    while(P>0){
        P/=2;
        b*=2;
    }
    if(a<b){
        cout<<N<<endl;
    }
    else cout<<b/2-1<<endl;
    

}