#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <climits>
#include <cstring>
#include <cassert>

#define rep(i, m, n) for(int i=int(m);i<int(n);i++)
#define all(c) begin(c),end(c)

template<typename T1, typename T2>
inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }

template<typename T1, typename T2>
inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }

typedef long long int ll;
using ll = long long int;
using ull = long long unsigned int;
using Int = long long int;
using uInt = long long unsigned int;
using Double = long double;
using namespace std;
#define INF (1 << 30) - 1
#define INFl (ll)5e15
#define DEBUG 0
#define dump(x)  cerr << #x << " = " << (x) << endl
#define MOD 1000000007


//edit
class Solve {
public:
    void solve() {
        Int N;
        cin >> N;
        string S;
        cin >> S;


        //あと一つオケば勝ち
        for (int i = 0; i + 3 < S.size(); ++i) {
            //o-o, -oo, oo-
            string sub = S.substr(i, 3);
//            cout << sub << endl;
            vector<string> win = {"oo-", "o-o", "-oo", "ooo"};
            for (auto e : win) {
                if (e == sub) {
                    cout << "O" << endl;
                    return;
                }
            }
        }

        vector<string> spl(1);
        for (int i = 0; i < S.size(); ++i) {
            if (S[i] == 'x') {
                spl.push_back("");
            } else {
                spl.back() += S[i];
            }
        }

        for (auto e : spl) {
            if (e.size() < 4) continue;
            if (e.front() == e.back() && e.front() == 'o' && e.size() % 2 == 1) {
                cout << "O" << endl;
                return;
            }
            for (int i = 1; i + 1 < e.size(); ++i) {
                if (e[i] == 'o') {
                    cout << "O" << endl;
                    return;
                }
            }
        }
        cout << "X" << endl;
    }
};


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    Int N;
    cin >> N;
    rep(i, 0, N)Solve().solve();


    return 0;
}