#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <climits>
#include <vector>
#include <numeric>
#include <complex>
#include <map>
#include <bitset>
#include <stack>
#include <queue>
#include <set>
using namespace std;

#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
const int Vec = 4;
const int Vecy[Vec] = {0,-1,0,1};
const int Vecx[Vec] = {1,0,-1,0};
const int Modd = 1000000007;

int main(){
	string str;
	cin >> str;
	
	if(str == "0"){
		cout << "X" << endl;
	}else if(str == "1"){
		cout << "O" << endl;
	}else if(str[str.length()-1] - '0' % 2 == 0){
		cout << "X" << endl;
	}else{
		cout << "O" << endl;
	}
    
    return 0;
}