#include <functional>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstring>
#include <string>
#include <vector>
#include <random>
#include <bitset>
#include <queue>
#include <cmath>
#include <stack>
#include <set>
#include <map>
typedef long long ll;
using namespace std;
const ll MOD = 1000000007LL;

int main() {
    cin.sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int t;
    cin >> t;

    while (t--) {
        int n;
        string s;
        cin >> n >> s;

        bool win = false;

        for (int i = 0; i < n - 2; i++) {
            string str = s.substr(i, 3);
            if (str == "ooo") win = true;
            if (str == "o-o") win = true;
            if (str == "oo-") win = true;
            if (str == "-oo") win = true;
        }

        for (int i = 0; i < n - 4; i++) {
            string str = s.substr(i, 5);
            if (str == "o-o-o") win = true;
        }

        cout << (win ? 'O' : 'X') << endl;
    }

    return 0;
}