#include <iostream>
using namespace std;
int main(){
  long long n;cin>>n;
  for(long long i = max(1LL,n-64); n+64 > i; i++){
    long long tmp = i;
    long long ham = 0;
    while(tmp){
      ham += tmp%2;
      tmp/=2;
    }
    if((ham^i) == n){
      cout << i << endl;
      return 0;
    }
  }
  cout << -1 << endl;
}