/*** author: yuji9511 ***/
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using lpair = pair<ll, ll>;
const ll MOD = 1e9+7;
const ll INF = 1e18;
#define rep(i,m,n) for(ll i=(m);i<(n);i++)
#define rrep(i,m,n) for(ll i=(m);i>=(n);i--)
#define printa(x,n) for(ll i=0;i<n;i++){cout<<(x[i])<<" \n"[i==n-1];};
void print() {}
template <class H,class... T>
void print(H&& h, T&&... t){cout<<h<<" \n"[sizeof...(t)==0];print(forward<T>(t)...);}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll T;
    cin >> T;
    while(T--){
        ll N;
        string S;
        cin >> N >> S;
        bool win = false;
        ll cnt = 0;
        ll cnt2 = 0;
        rep(i,0,N){
            if(S[i] == 'o'){
                cnt++;
            }else{
                cnt = 0;
            }
            if(S[i] == '-'){
                cnt2++;
            }else{
                cnt2 = 0;
            }
            if(cnt == 3) win = true;
            if(cnt == 2){
                if((i - 2 >= 0 && S[i-2] == '-') || (i+1 < N && S[i+1] == '-')) win = true;
            }
            if(cnt == 1){
                if(i - 2 >= 0 && i+1 < N && S[i-2] == '-' && S[i-1] == '-' && S[i+1] == '-') win = true;
                if(i - 1 >= 0 && i+2 < N && S[i-1] == '-' && S[i+1] == '-' && S[i+2] == '-') win = true;
            }
            if(cnt2 % 2 == 1){
                if(i+1 < N && i-cnt2 >= 0 && S[i-cnt2] == 'o' && S[i+1] == 'o') win = true;
            }
        }
        rep(i,1,N-1){
            if(S[i-1] == 'o' && S[i+1] == 'o' && S[i] == '-') win = true;
        }

        if(win){
            print("O");
        }else{
            print("X");
        }

    }
    

}