#include<bits/stdc++.h>
//ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//clock_t start=clock();clock_t end=clock();cout<<(double)(end-start)/CLOCKS_PER_SEC<<endl;
using namespace std;
typedef int ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef pair<int,int> pii;
typedef pair<pii,int> ppii;
typedef pair<int,pii> pipi;
typedef pair<ll,ll> pll;
typedef pair<pll,ll> ppll;
typedef pair<ll,pll> plpl;
typedef tuple<ll,ll,ll> tl;
typedef pair<double,double> pdd;
typedef vector<vector<ll>> mat;
ll mod=1000000007;
ll mod2=998244353;
ll mod3=1000003;
ll mod4=998244853;
ll mod5=1000000009;
ll inf=1000000001;
double pi=3.141592653589793238462643383279L;
double eps=1e-14;
#define rep(i,m,n) for(ll i=m;i<n;i++)
#define rrep(i,n,m) for(ll i=n;i>=m;i--)
#define srep(itr,st) for(auto itr=st.begin();itr!=st.end();itr++)
#define mrep(itr,mp) for(auto itr=mp.begin();itr!=mp.end();itr++)
#define Max(a,b) a=max(a,b)
#define Min(a,b) a=min(a,b)
int dh[4]={1,-1,0,0};
int dw[4]={0,0,1,-1};
int ddh[8]={-1,-1,-1,0,0,1,1,1};
int ddw[8]={-1,0,1,-1,1,-1,0,1};
ll gcd(ll a,ll b){
    if(a<b)swap(a,b);
    if(b==0)return a;
    if(a%b==0)return b;
    return gcd(b,a%b);
}
ll lcm(ll a,ll b){
    ll c=gcd(a,b);
    return a*b/c;
}
ll Pow(ll n,ll k){
    ll ret=1;
    ll now=n;
    while(k>0){
        if(k&1)ret*=now;
        now*=now;
        k/=2;
    }
    return ret;
}
ll beki(ll n,ll k,ll md){
  ll ret=1;
  ll now=n;
    now%=md;
  while(k>0){
    if(k%2==1){
      ret*=now;
      ret%=md;
    }
    now*=now;
    now%=md;
    k/=2;
  }
  return ret;
}
ll gyaku(ll n,ll md){
  return beki(n,md-2,md);
}
ll popcount(ll n){
    ll ret=0;
    ll u=n;
    while(u>0){
        ret+=u%2;
        u/=2;
        
    }
    return ret;
}
int main(){
    ios::sync_with_stdio(false);cin.tie(0);
    int t;cin>>t;
    while(t--){
        int n;cin>>n;
        string s;cin>>s;
        int sum[n+1];
        sum[0]=0;
        rep(i,0,n){
            sum[i+1]=sum[i];
            if(s[i]=='o')sum[i+1]++;
        }
        bool win=false;
        int l=0,r=0;
        for(;;){
            while(r<n&&s[r]=='x')r++;
            if(r==n)break;
            l=r;
            while(r<n&&s[r]!='x')r++;
            if(r-l>=3){
                if(s[l]=='o'&&s[r-1]=='o'&&(r-l)%2)win=true;
                if(r-l>=4&&sum[r-1]-sum[l+1]>=1)win=true;
            }
        }
        rep(i,0,n-2){
            string t=s.substr(i,3);
            if(t=="oo-"||t=="-oo")win=true;
        }
        if(win)cout<<"O"<<endl;
        else cout<<"X"<<endl;
    }
}