#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <queue>
#include <map>
#include <stack>
#include <bitset>
#include <numeric> //lcm
#include <iomanip> //double精度 setprecision


#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = n-1; i >= 0; --i)
#define rep1(i,n) for(int i = 1; i <= (n); ++i)
#define all(vec) (vec).begin(),(vec).end()

#define debug(vec) for(auto v : vec) cout << v << " "; cout << endl;
#define debug2D(vec2D) for(auto vec : vec2D) { for (auto v : vec) cout << v << " "; cout << endl; } 

using namespace std;

typedef long long ll;

const ll INF = 1000000000; //10^10
//const ll MOD = 998244353;
const ll MOD = 1000000007;

template<class T>inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } else return false; }
template<class T>inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } else return false; }

int main() {
	int t;
	cin >> t;

	rep(test, t) {
		int n; cin >> n;
		string s; cin >> s;

		vector<int> ss;
		if (s.find("ooo") != string::npos || s.find("o-o") != string::npos || s.find("-oo") != string::npos || s.find("oo-") != string::npos) cout << 'O' << endl;
		else if (s.find("-o--") != string::npos || s.find("--o-") != string::npos)cout << 'O' << endl;
		else cout << 'X' << endl;
	}
}