#include <bits/stdc++.h>
#include <iomanip>
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()
#define fi first
#define se second
typedef long long ll;
typedef vector<ll> vec;
typedef vector<vec> mat;

ll N,M,H,W,K,Q,A,B;
string S;
const ll MOD = 998244353;
//const ll MOD = (1e+9) + 7;
const ll INF = 1LL<<60;
typedef pair<ll, ll> P;

int main() {
    cin>>Q;
    rep(roop,Q){
        //cout<<roop<<endl;
        cin>>N>>S;
        string T = "x";
        T.append(S);
        T.push_back('x');
        N += 2;
        vec x_id(0);
        rep(i,N) if(T[i] == 'x') x_id.push_back(i);
        int sz = x_id.size();
        rep(i, sz - 1){
            int l = x_id[i] + 1, r = x_id[i + 1];
            //cout<<l<<' '<<r<<endl;
            if(r - l >= 3) {
                int num = 0;
                reps(j, l + 1, r - 1) num += T[j] == 'o';
                if (r - l == 3) {
                    num += T[l] == 'o';
                    num += T[r - 1] == 'o';
                    if (num >= 2) {
                        cout << 'O' << endl;
                        break;
                    }
                } else if (num > 0 || (T[l] == 'o' && T[r - 1] == 'o' && ((r - l) & 1))) {
                    cout << 'O' << endl;
                    break;
                }
            }
            if(i == sz - 2){
                cout<<'X'<<endl;
            }
        }
    }
}