#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

int main() {
    i64 n;
    cin >> n;
    n++;
    for (i64 i = 1; i < i64(1) << 32; i <<= 1) {
        if (i == n) {
            cout << "X" << endl;
            return 0;
        }
    }
    cout << "O" << endl;
}