#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
using namespace std;

int main() {
    int T;
    cin >> T;
    rep(i, T) {
        int N;
        string S;
        cin >> N >> S;
        if (N <= 2) {
            cout << "X" << endl;
            continue;
        }
        bool flag = false;
        rep(i, N - 2) {
            string s = "";
            s += S[i];
            s += S[i + 1];
            s += S[i + 2];
            // cout << s << endl;
            if(s == "ooo" || s=="oo-" || s=="o-o" || s=="-oo"){
                flag = true;
                break;
            }
        }
        cout << (flag?"O":"X") << endl;
    }
}