#include <iostream>
#include <string>

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

    int len = 0, c1 = -1, c2 = -1;
    bool ans = false;

    while (n--) {
        char c;
        std::cin >> c;

        if (c == 'x') {
            len = 0;
            c1 = c2 = -1;

        } else {
            ++len;
            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::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;
}