#include <bits/stdc++.h>
using namespace std;
#define rep(i, l, r) for (int i = (int)(l); i < (int)(r); i++)
#define rrep(i, r, l) for (int i = (int)(r); i > (int)(l); i--)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()

void solve() {
    long long n;
    cin >> n;
    long long power = 1;
    rep(i, 0, 32) {
        power <<= 1;
        if (power - 1 == n) {
            cout << "X" << '\n';
            return;
        }
    }

    cout << "O" << '\n';
}

int main() {
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}