#include <iostream>
#include <array>
#include <algorithm>
#include <vector>
#include <bitset>
#include <set>
#include <unordered_set>
#include <cmath>
#include <complex>
#include <deque>
#include <iterator>
#include <numeric>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <string>
#include <tuple>
#include <utility>
#include <limits>
#include <iomanip>
#include <functional>
#include <cassert>
using namespace std;

using ll=long long;
template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;
using vll = V<ll>;
using vvll = V<vll>;
#define rep(i, k, n) for (ll i=k; i<(ll)n; ++i)
#define REP(i, n) rep(i, 0, n)
#define ALL(v) v.begin(),v.end()
template < class T > inline bool chmax(T& a, T b) {if (a < b) { a=b; return true; } return false; }
template < class T > inline bool chmin(T& a, T b) {if (a > b) { a=b; return true; } return false; }
#define DEBUG_VLL(vec) REP(sz, vec.size()) std::cerr<<vec[sz]<<(sz==vec.size()-1?'\n':' ');

const long long MOD = 1000000007;
const long long HIGHINF = (long long)1e18;
const int INF = (int)1e9;

int t;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> t;
    while (t-->0) {
        int n; cin >> n;
        string s; cin >> s;
        int tmp = 0;
        char prevc = 'x';
        bool ooo = false;
        for (int i = 0; i < n; i++) {
            if (s[i] == 'o') {
                if (i + 1 < n && s[i + 1] == 'o' && i + 2 < n && s[i + 2] == 'o') {
                    cout << "O\n";
                    ooo = true;
                    break;
                }

                if (i + 1 < n && s[i + 1] == '-' && i + 2 < n && s[i + 2] == 'o') {
                    cout << "O\n";
                    ooo = true;
                    break;
                }

                if (i + 1 < n && s[i + 1] == 'o' && ((i - 1 >= 0 && s[i - 1] == '-') || (i + 2 < n && s[i + 2] == '-'))) {
                    cout << "O\n";
                    ooo = true;
                    break;
                }

                if (i - 1 >= 0 && s[i - 1] == '-' && i + 1 < n && s[i + 1] == '-' && ((i - 2 >= 0 && s[i - 2] == '-') || (i + 2 < n && s[i + 2] == '-'))) {
                    cout << "O\n";
                    ooo = true;
                    break;
                }

                if (prevc == 'o' && (tmp & 1)) {
                    cout << "O\n";
                    ooo = true;
                    break;
                }
            }

            if (s[i] == '-') tmp++;
            else tmp = 0, prevc = s[i];
        }

        if (!ooo) cout << "X\n";
    }
    return 0;
}