#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  auto solve = [] () {
    int n;
    cin >> n;
    string s;
    cin >> s;
    for (int i = 0; i + 2 < n; i++) {
      if (s.substr(i, 3) == "ooo") return "O\n";
    }
    for (int i = 0; i < n; i++) {
      if (s[i] == '-') {
        s[i] = 'o';
        for (int j = max(0, i - 2); j <= i; j++) {
          if (s.substr(j, 3) == "ooo") return "O\n";
        }
        for (int j = max(0, i - 3); j <= i; j++) {
          if (s.substr(j, 4) == "-oo-") return "O\n";
        }
        s[i] = '-';
      }
    }
    return "X\n";
  };
  int t;
  cin >> t;
  while (t--) cout << solve();
  return 0;
}