#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000

int main(){
	
	long long X;
	cin>>X;
	
	rep(i,61){
		long long t = X^i;
		if(t==0)continue;
		int c = 0;
		rep(j,61){
			if((t>>j)&1)c++;
		}
		if(c==i){
			cout<<t<<endl;
			return 0;
		}
	}
	cout<<-1<<endl;
	
    return 0;
}