/* -*- coding: utf-8 -*-
 *
 * 1450.cc:  No.1450 nahco314's First Problem - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int BN = 61;

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

inline int bnum(ll a) {
  int c = 0;
  for (; a > 0; a >>= 1) c += (a & 1);
  return c;
}

/* main */

int main() {
  ll x;
  scanf("%lld", &x);

  for (int m = 0; m < BN; m++) {
    ll n = x ^ m;
    if (bnum(n) == m) {
      printf("%lld\n", n);
      return 0;
    }
  }

  puts("-1");
  return 0;
}