#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

map<string, int> memo[2];
int test(string &s, int t) {
    if (memo[t].count(s))return memo[t][s];

    int &res = memo[t][s];

    int n = sz(s);
    rep(i, n - 2) {
        int cnt = 0;
        FOR(j, i, i + 3) if (s[j] == 'o')cnt++;
        if (cnt == 3) return res = 1;
    }

    int cnt = 0;
    rep(i, n)if (s[i] == '-') {
        s[i] = t ? 'x' : 'o';
        int ret = test(s, 1 - t);
        s[i] = '-';
        if (t && !ret)return res = 0;
        if (!t && ret)return res = 1;
        cnt++;
    }
    if (cnt == 0)return res = 0;
    return res = t;
}

void solve() {

    //for (int S = 0; S < (1 << 7); ++S) {
    //    string T(7, '-');
    //    rep(i, 7)if (S >> i & 1)T[i] = 'o';
    //    cout << test(T, 0) << ' ' << T << endl;
    //}

    string V[] = { "--o-", "-o--", "oo-", "-oo", "ooo" };

    int T;
    cin >> T;
    while (T--) {
        int N;
        string S;
        cin >> N >> S;
        char ans = [&] {
            for (auto U : V) {
                rep(i, N - sz(U) + 1) {
                    int win = 1;
                    rep(j, sz(U)) if (S[i + j] != U[j])win = 0;
                    if (win) return 'O';
                }
            }
            int pre = N;
            rep(i, N) {
                if (S[i] == 'o') {
                    int d = i - pre;
                    if (d > 1 && d % 2 == 0) return 'O';
                    pre = i;
                } else if (S[i] == 'x') {
                    pre = N;
                }
            }
            return 'X';
        }();
        cout << ans << endl;
    }
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}