#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>

#define rep(i,n) for(i=0; i<n; ++i)
#define in(a) cin >> a
#define out(a,b) cout << a << b
using namespace std;
using lint = long long;

int main(void){
    int i, j;
    int n, m;
    in(n);
    in(m);
    int x = max(n,m), y = min(n,m), r = 1;
    while(1){
        if(r<=x&&x<r*2)   break;
        r*=2;
    }
    int ans = min(y, r-1);
    cout << ans << endl;

    return 0;
}