#include <iostream>
#include <string>

using namespace std;
string s[6] = {"--o-","-o--","oo-","o-o","-oo","ooo"};
bool ch(string st,string u){
    int i,j,n = st.size(),k = u.size();
    for(i=0;i<n;i++){
        for(j=0;j<k;j++){
            if(i + j>=n || st[i + j]!=u[j]) break;
            if(j==k - 1) return true;
        }
    }
    return false;
}

int main(){
    int i,t;
    cin >> t;
    while(t){
        t--;
        int n; string st;
        cin >> n >> st;
        for(i=0;i<6;i++){
            if(ch(st,s[i])){
                cout << "O" << endl;
                break;
            }
            if(i==5){
                cout << "X" << endl;
            }
        }
    }
}