#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,m,n) for(int i=m; i<n; ++i)
#define repl(i,m,n) for(ll i=m; i<n; ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()

int main(){
    ll X;
    cin >> X;

    for(ll m = 1LL; m < 64LL; ++m){
        ll n = X ^ m;
        ll cnt = 0;
        rep(i, 0, 64){
            if(n & (1LL << i)){
                cnt++;
            }
        }
        if(cnt == m){
            cout << n << endl;
            return 0;
        }
    }
    cout << -1 << endl;
    return 0;
}