#include <iostream>
#include <string>

void solve() {
    int n;
    std::string s;
    std::cin >> n >> s;

    auto judge = [&]() -> bool {
        for (int i = 0; i < n; ++i) {
            if (s.substr(i, 3) == "ooo" ||
                s.substr(i, 4) == "-oo-") {
                return true;
            }
        }
        return false;
    };

    bool ans = judge();
    for (int i = 0; i < n; ++i) {
        if (s[i] != '-') continue;
        s[i] = 'o';
        if (judge()) ans = true;
        s[i] = '-';
    }

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

int main() {
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int q;
    std::cin >> q;
    while (q--) solve();

    return 0;
}