#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define P pair<ll,ll>
#define FOR(I,A,B) for(ll I = ll(A); I < ll(B); ++I)
#define FORR(I,A,B) for(ll I = ll((B)-1); I >= ll(A); --I)
#define TO(x,t,f) ((x)?(t):(f))
#define SORT(x) (sort(x.begin(),x.end())) // 0 2 2 3 4 5 8 9
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin()) //xi>=v  x is sorted
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin()) //xi>v  x is sorted
#define NUM(x,v) (POSU(x,v)-POSL(x,v))  //x is sorted
#define REV(x) (reverse(x.begin(),x.end())) //reverse
ll gcd(ll a,ll b){if(a%b==0)return b;return gcd(b,a%b);}
ll lcm(ll a,ll b){ll c=gcd(a,b);return ((a/c)*(b/c)*c);}
#define NEXTP(x) next_permutation(x.begin(),x.end())
const ll INF=ll(1e16)+ll(7);
const ll MOD=1000000007LL;
#define out(a) cout<<fixed<<setprecision((a))
//tie(a,b,c) = make_tuple(10,9,87);
#define pop_(a) __builtin_popcount((a))
ll keta(ll a){ll r=0;while(a){a/=10;r++;}return r;}
ll ketawa(ll a){ll r=0;while(a){r+=a%10;a/=10;}return r;}


int main(){
  ll T;
  cin >> T;
  FOR(t,0,T){
    ll n;
    string s;
    cin >> n >> s;
    bool o_win = false;
    FOR(i,0,n-2){
      string k = s.substr(i,3);
      if(k=="-oo"||k=="oo-"||k=="ooo")o_win=true;
    }
    FOR(i,0,n-3){
      string k = s.substr(i,4);
      if(k=="-o--"||k=="--o-"||k=="ooo")o_win=true;
    }
    if(o_win){
      cout << "O" << "\n";
    }else{
      cout << "X" << "\n";
    }
  }
}