#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;

bool solve(string &S){
	int N = S.size();
	
	for(int i = 0; i < N - 2; i++){
		string x;
		
		x += S[i];
		x += S[i+1];
		x += S[i+2];
		
		if(x == "ooo") return true;
		if(x == "oo-") return true;
		if(x == "o-o") return true;
		if(x == "-oo") return true;
	}
	
	return false;
}

signed main(){
	cout<<fixed<<setprecision(10);
	
	int T;
	
	cin>>T;
	
	for(int _ = 0; _ < T; _++){
		int N;
		string S;
		
		cin>>N>>S;
		
		if(solve(S)) cout<<"O"<<endl;
		else cout<<"X"<<endl;
	}
	
	
	return 0;
}