#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int main() {
	long long x;
	long long o = 1, m = 2000000000000000000;
	cin >> x;
	for (long long i = 0; i < 64; i++) {
		long long x1 = x ^ i;
		long long co = 0;
		for (int j = 0; j < 64; j++) {
			if ((o << j) & x1) {
				co++;
			}
			else {
			}
		}
		if (co == i && x1 > 0) {
			cout << x1 << endl;
			return 0;
		}
	}
	cout << -1 << endl;
	return 0;
}