#include<bits/stdc++.h>
using namespace std;
using ll = long long;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 710
#endif

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n;
	cin >> n;
	bool f = false;
	int temp = 2;
	for(int i = 0; i < 31; i++){
		temp *= 2;
		if(n == temp - 1){
			f = true;
		}
	}
	cout << (f ? "X" : "O") << endl;
}