/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2021.03.31 23:37:47
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int hamingu(ll n) {
    int ans = 0;
    while(n) {
        if (n & 1) ans++;
        n >>= 1;
    }
    return ans;
}
int main() {
    ll x;cin >> x;
    for (int i = 1; i <= 64; i++) {
        if (hamingu(x ^ i) == i) {
            cout << (x ^ i) << endl;
            return 0;
        }
    }
    cout << -1 << endl;
    return 0;
}