#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll X, v;
    cin >> X;
    for(int i = 0; i < 62; i++){
        v = X ^ i;
        if(__builtin_popcountll(v) == i && v <= 2000000000000000000ll){
            cout << v << '\n';
            return 0;
        }
    }
    cout << -1 << '\n';
}