#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

void solve(){
  int N;
  string S;
  cin>>N>>S;

  for(int i=2;i<N;i++){
    if(S[i-2]=='o'&&S[i]=='o'&&S[i-1]!='x'){
      cout<<'O'<<"\n";
      return;
    }
  }
  for(int i=0;i+1<N;i++){
    if(S[i]=='o'&&S[i+1]=='o'){
      if((i-1>=0&&S[i-1]!='x')||(i+2<N&&S[i+2]!='x')){
        cout<<'O'<<"\n";
        return;
      }
    }
    if((S[i]=='o'&&S[i+1]=='-')||(S[i]=='-'&&S[i+1]=='o')){
      if(i-1>=0&&S[i-1]=='-'&&i+2<N&&S[i+2]=='-'){
        cout<<'O'<<"\n";
        return;
      }
    }
  }

  int num=0;
  char pre='x';
  for(int i=0;i<N;i++){
    if(S[i]=='x'){
      num=0;
      pre='x';continue;
    }
    if(S[i]=='o'){
      if(num%2&&pre=='o'){
        cout<<"O"<<"\n";
        return ;
      }
      pre='o';
      num=0;
    }else num++;
  }

  cout<<'X'<<"\n";
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int T;
  cin>>T;
  rep(i,T) solve();

  return 0;
}