#include <iostream>
#include <string>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <queue>
#include <stack>
#include <functional>
#include <bitset>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef pair<ll,ll> P;
typedef vector<P> vpl;
typedef tuple<ll,ll,ll> tapu;
#define rep(i,n) for(ll i=0; i<(n); i++)
#define REP(i,a,b) for(ll i=(a); i<(b); i++)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const int inf = 1<<30;
const ll linf = 1LL<<62;
const int MAX = 510000;
ll dy[8] = {0,1,0,-1,1,-1,1,-1};
ll dx[8] = {1,0,-1,0,1,-1,-1,1};
const double pi = acos(-1);
const double eps = 1e-7;
template<typename T1,typename T2> inline bool chmin(T1 &a,T2 b){
	if(a>b){
		a = b; return true;
	}
	else return false;
}
template<typename T1,typename T2> inline bool chmax(T1 &a,T2 b){
	if(a<b){
		a = b; return true;
	}
	else return false;
}
template<typename T1,typename T2> inline void print2(T1 a, T2 b){cout << a << " " << b << endl;}
template<typename T1,typename T2,typename T3> inline void print3(T1 a, T2 b, T3 c){
	cout << a << " " << b << " " << c << endl;
}
const int mod = 1e9 + 7;
//const int mod = 998244353;

void solve(){
	ll n; cin >> n;
	string t; cin >> t;
	string s = "@@" + t + "@@";
	REP(i,2,n+2){
		if(s[i]=='x' || s[i]=='-') continue;
		if(s[i+1]=='o'){
			if(s[i-1]=='o'){
				puts("O");
				return;
			}
			if((s[i-1]=='x'||s[i-1]=='@') && (s[i+2]=='x'||s[i+2]=='@')) continue;
			else{
				puts("O");
				return;
			}
		}else if(s[i+1]=='-'){
			if(s[i+2]=='o'){
				puts("O");
				return;
			}
			if(s[i-1]=='x' || s[i-1]=='@'){
				continue;
			}
			if(s[i-1]=='o'){
				puts("O");
				return;
			}
			if(s[i-2]=='-'||s[i+2]=='-'||s[i-2]=='o'||s[i+2]=='o'){
				puts("O");
				return;
			}
		}
	}
	puts("X");
}


int main(){
	ll t; cin >> t;
	while(t--){
		solve();
	}
}