#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double D;
typedef pair<ll,ll> P;
#define M 1000000007
#define F first
#define S second
#define PB push_back
#define INF 1000000000000000
ll n;
int main(void){
    cin>>n;
    for(ll i=0;i<=32;i++){
		if(n==(1LL<<i)-1){
			printf("X\n");
			return 0;
		}
	}
	printf("O\n");
}