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

int main() {
    long long X;
    cin >> X;
    for(int i = 1; i <= 62; i++) {
        long long ans = (X^i);
        if(__builtin_popcountll(ans) == i) {
            cout << ans << endl;
            return 0;
        }
    }
    cout << -1 << endl;
}