#include <bits/stdc++.h>

using namespace std;

using ll = long long;

char solve(int n, const string& s) {
    // 残り0 or 1個で勝ち
    int cnt = 0;
    for (int i = 0; i < n; ++i) {
        if (s[i] == 'x') continue;
        bool f = false;
        if (i + 2 < n) f |= (s[i + 1] == 'o' && s[i + 2] == 'o');
        if (i > 0 && i + 1 < n) f |= (s[i - 1] == 'o' && s[i + 1] == 'o');
        if (i > 1) f |= (s[i - 2] == 'o' && s[i - 1] == 'o');
        cnt += f;
    }
    if (cnt > 0) return 'O';

    // o-o or o---o or o-----o or o-------o or ...
    vector<int> even, odd;
    for (int i = 0; i < n; ++i) {
        if (s[i] == 'x') {
            even.clear();
            odd.clear();
            continue;
        }

        if (s[i] == 'o') {
            if (i % 2 == 0) {
                if (!even.empty()) return 'O';
                even.push_back(i);
            } else {
                if (!odd.empty()) return 'O';
                odd.push_back(i);
            }
        }
    }

    // .o.. or ..o.
    for (int i = 0; i < n; ++i) {
        if (s[i] == 'o') {
            if (i > 0 && i + 2 < n) {
                bool f = true;
                for (int j = i - 1; j < i + 3; ++j) {
                    if (s[j] == 'x') {
                        f = false;
                        break;
                    }
                }
                if (f) return 'O';
            }

            if (i > 1 && i + 1 < n) {
                bool f = true;
                for (int j = i - 2; j < i + 2; ++j) {
                    if (s[j] == 'x') {
                        f = false;
                        break;
                    }
                }
                if (f) return 'O';                
            }
        }
    }

    return 'X';
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t;
    cin >> t;
    for (int i = 0; i < t; ++i) {
        int n;
        string s;
        cin >> n >> s;
        cout << solve(n, s) << "\n";
    }
    return 0;
}