#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
const ll MOD = 998244353;
const ll INF = 2147483647;
const ll LINF = 9223372036854775807;
#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()

string p[3]={"oo-","o-o","-oo"};

int main(){
	int t; cin >> t;
	while(t--){
		int n; cin >> n;
		string s; cin >> s;
		int m=0;
		REP(i,n-2){
			REP(j,3){
				bool f=1;
				REP(k,3)if(p[j][k]!=s[i+k])f=0;
				if(f){
					m++;
					i+=2;
					break;
				}
			}
		}
		bool win=0;
		REP(i,n-2) if(s[i]=='o'&&s[i+1]=='o'&&s[i+2]=='o') win=1;
		if(win||m>=1)
			cout << 'O' << endl;
		else
			cout << 'X' << endl;
	}
	return 0;
}