#include <bits/stdc++.h>

using namespace std;
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)

typedef long long ll;
typedef pair<ll, ll> P;
const ll INF = 1LL<<60;

ll gcd(ll a, ll b) {
  if(b == 0) return a;
  return gcd(b, a % b);
}

template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

ll modpow(ll a, ll n, ll mod) {
  ll res = 1;
  while (n > 0) {
    if (n & 1) res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int T;
  cin >> T;
  vector<bool> ans(T);

  rep(t, T){ans[t] = false;}

  rep(t, T){

    int N;
    cin >> N;
    string s;
    cin >> s;

    rep(i, N){
      
      if(i+3 <= N){
        
        if(s.substr(i, 3) == "ooo") ans[t] = true;
        if(s.substr(i, 3) == "-oo") ans[t] = true;
        if(s.substr(i, 3) == "o-o") ans[t] = true;
        if(s.substr(i, 3) == "oo-") ans[t] = true;

      }

      if(i+4 <= N){

        if(s.substr(i, 4) == "--o-") ans[t] = true;
        if(s.substr(i, 4) == "-o--") ans[t] = true;
 
      }

    }

  }

  rep(t, T){
    if(ans[t]){
      cout << "O" << endl;
    }else{
      cout << "X" << endl;
    }
  }

  return 0;
}