#include <iostream>
#include <algorithm>
#include <string>

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

    bool ans = false;
    for (int i = 0; i < n; ++i) {
        if (s.substr(i, 4) == "--o-" ||
            s.substr(i, 4) == "-o--") ans = true;
    }

    for (int i = 0; i < 2; ++i) {
        int c1 = -1, c2 = -1;

        for (auto c : s) {
            if (c == 'x') {
                c1 = c2 = -1;

            } else {
                int c0 = (c == 'o');
                if ((c1 == 1 && c2 == 1) ||
                    (c0 == 1 && c2 == 1) ||
                    (c0 == 1 && c1 == 1 && c2 != -1)) {
                    ans = true;
                }

                if (c2 == 1) {
                    c0 = 1;
                    c1 = -1;
                }

                c2 = c1;
                c1 = c0;
            }
        }

        std::reverse(s.begin(), s.end());
    }

    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;
}