#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> l_l;
typedef pair<int, int> i_i;
template<class T>
inline bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}

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

const long double EPS = 1e-10;
const long long INF = 1e18;
const long double PI = acos(-1.0L);
//const ll mod = 1000000007;

bool check(string S) {
    ll num = 0;
    for(int i = 0; i < S.size(); i++) {
        if(S[i] == 'o') num++;
    }
    if(num >= 3) return true;
    if(num <= 1) return false;
    if(S[0] == 'o' and S.back() == 'o') return false;
    return true;
}

void solve() {
    ll N;
    string S;
    cin >> N >> S;
    S = "x" + S + "x";
    ll Last = 0;
    for(int i = 1; i < S.size(); i++) {
        if(S[i] == 'x') {
            if(i - Last - 1 > 0 and check(S.substr(Last+1, i-Last-1))) {
                cout << "O" << endl;
                return;
            }
            Last = i;
        }
    }
    cout << "X" << endl;
}

int main() {
    //cout.precision(10);
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    while(N--) solve();
    return 0;
}