#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;

vector<string> split(const string &s, const string &delimiter) {
  vector<string> res;
  int pos = 0;
  while (true) {
    int del_pos = s.find(delimiter, pos);
    if (del_pos == s.npos) break;
    res.emplace_back(s.substr(pos, del_pos - pos));
    pos = del_pos + delimiter.length();
  }
  res.emplace_back(s.substr(pos));
  return res;
}

void solve() {
  int n; string s; cin >> n >> s;
  for (const string &board : split(s, "x")) {
    int cnt = count(ALL(board), 'o');
    if (cnt >= 3) {
      cout << "O\n";
      return;
    }
    if (cnt == 0) continue;
    int m = board.length();
    REP(i, m) {
      if (board[i] == 'o' && ((i > 0 && i + 2 < m) || (i - 2 >= 0 && i + 1 < m))) {
        cout << "O\n";
        return;
      }
    }
    if (cnt == 1) continue;
    REP(i, m - 1) {
      if (board[i] == 'o' && board[i + 1] == 'o' && (i > 0 || i + 2 < m)) {
        cout << "O\n";
        return;
      }
    }
    REP(i, m - 2) {
      if (board[i] == 'o' && board[i + 2] == 'o') {
        cout << "O\n";
        return;
      }
    }
    if (board[0] == 'o' && board[m - 1] == 'o' && (m & 1)) {
      cout << "O\n";
      return;
    }
  }
  cout << "X\n";
}

int main() {
  int t; cin >> t;
  while (t--) solve();
  return 0;
}