#include <bits/stdc++.h>
using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  
  int t;
  cin >> t;
  
  for (int i = 0; i < t; i++) {
    int n;
    string s;
    cin >> n >> s;
    bool flag = false;
    for (int j = 0; j < n; j++) {
      string a, b, c;
      if (n - j >= 3) {
        a = s.substr(j, 3);
        if (a == "ooo" || a == "-oo" || a == "o-o" || a == "oo-") {
          cout << "O\n";
          flag = true;
          break;
        }
      }
      if (n - j >= 4) {
        b = s.substr(j, 4);
        if (b == "--o-" || b == "-o--") {
          cout << "O\n";
          flag = true;
          break;
        }
      }
      if (n - j >= 5) {
        c = s.substr(j, 5);
        if (c == "--o--") {
          cout << "O\n";
          flag = true;
          break;
        }
      }
    }
    if (!flag) cout << "X\n";
  }
}