#include<bits/stdc++.h>
#include <atcoder/twosat>
using namespace std;
using namespace atcoder;
using ll = long long int;
using ld = long double;
const ll MAX = 5000000000000000000;
const ld PI = 3.14159265358979;
const ll MOD = 0;//2024948111;
ld dotorad(ld K){return PI * K / 180.0;}
ld radtodo(ld K){return K * 180.0 / PI;}
mt19937 mt;
void randinit(){srand((unsigned)time(NULL));mt = mt19937(rand());}
int main(){
    ll T;
    cin >> T;
    for(ll t = 0;t < T;t++){
        ll N;
        char ans = 'X';
        string S;
        cin >> N >> S;
        for(ll i = 0;i < N - 2;i++){
            if(S[i] == 'o' && S[i + 1] == 'o' && S[i + 2] == 'o') ans = 'O';
            if(S[i] == 'o' && S[i + 1] == '-' && S[i + 2] == 'o') ans = 'O';
            if(S[i] == 'o' && S[i + 1] == 'o' && S[i + 2] == '-') ans = 'O';
            if(S[i] == '-' && S[i + 1] == 'o' && S[i + 2] == 'o') ans = 'O';
        }
        for(ll i = 0;i < N - 3;i++){
            if(S[i] == '-' && S[i + 1] == 'o' && S[i + 2] == '-' && S[i + 3] == '-') ans = 'O';
            if(S[i] == '-' && S[i + 1] == '-' && S[i + 2] == 'o' && S[i + 3] == '-') ans = 'O';
        }
        for(ll i = 0;i < N - 1;i++){
            if(S[i] == 'o' && S[i + 1] == '-'){
                ll p = i;
                i++;
                while(S[i] == '-') i++;
                if(S[i] == 'o' && (i - p) % 2 == 0){
                    ans = 'O';
                }
            }
        }
        for(ll i = 0;i < N - 4;i++){
            if(S[i] == 'o' && S[i + 1] == '-' && S[i + 2] == '-' && S[i + 3] == '-' && S[i + 4] == 'o') ans = 'O';
        }
        cout << ans << endl;
    }
}