#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<iomanip>
#include<math.h>
#include<complex>
#include<queue>
#include<deque>
#include<stack>
#include<map>
#include<set>
#include<bitset>
#include<functional>
#include<assert.h>
#include<numeric>
using namespace std;
#define REP(i,m,n) for(int i=(int)(m) ; i < (int) (n) ; ++i )
#define rep(i,n) REP(i,0,n)
using ll = long long;
constexpr int inf=1e9+7;
constexpr ll longinf=1LL<<60 ;
constexpr ll mod=1e9+7 ;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t;
    cin>>t;
    while(t--){
        int n;
        cin>>n;
        string s;
        cin>>s;
        bool win=false;
        rep(i,n-2){
            if(s[i]=='o'&&s[i+1]=='o'&&s[i+2]=='o')win=true;
            if(s[i]=='o'&&s[i+1]=='o'&&s[i+2]=='-')win=true;
            if(s[i]=='o'&&s[i+1]=='-'&&s[i+2]=='o')win=true;
            if(s[i]=='-'&&s[i+1]=='o'&&s[i+2]=='o')win=true;
        }
        rep(i,n-3){
            if(s[i]=='-'&&s[i+1]=='-'&&s[i+2]=='o'&&s[i+3]=='-')win=true;
            if(s[i]=='-'&&s[i+1]=='o'&&s[i+2]=='-'&&s[i+3]=='-')win=true;
        }
        rep(i,n-4){
            if(s[i]=='o'&&s[i+1]=='-'&&s[i+2]=='-'&&s[i+3]=='-'&&s[i+4]=='o')win=true;
        }
        if(win)cout<<"O"<<endl;
        else cout<<"X"<<endl;
    }
    return 0;
}