#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

int main() {
    int t; cin >> t;
    for (int i = 0; i < t; i++) {
        int n; cin >> n;
        string s; cin >> s;
        bool ok = false;
        for (int i = 0; i < n - 2; i++) {
            if (s[i] == 'o' && s[i + 1] == 'o' && s[i + 2] == '-') {
                ok = true;
            }
            else if (s[i] == '-' && s[i + 1] == 'o' && s[i + 2] == 'o') {
                ok = true;
            }
            else if (s[i] == 'o' && s[i + 1] == 'o' && s[i + 2] == 'o') {
                ok = true;
            }
            else if (s[i] == 'o' && s[i + 1] == '-' && s[i + 2] == 'o') {
                ok = true;
            }
        }
        for (int i = 0; i < n - 4; i++) {
            if (s[i] == '-' && s[i + 1] == '-' && s[i + 2] == 'o' && s[i + 2] == '-' && s[i + 2] == '-') {
                ok = true;
            }
        }
        if (ok) {
            puts("O");
        }
        else {
            puts("X");
        }
    }
    return 0;
}