#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(n); ++i)
using namespace std;
using ll = long long;

string solve(int N, string S) {
    for (int i=0; i<N-2; ++i) {
        string s_ = S.substr(i, 3);
        if ((s_ == "ooo") ||
            (s_ == "-oo") ||
            (s_ == "o-o") ||
            (s_ == "oo-")) {
                return "O";
        } 
    }
    for (int i=0; i<N-3; ++i) {
        string s_ = S.substr(i, 4);
        if (s_ == "--o-" || s_ == "-o--") return "O";
    }
    int hy = 0;
    for (int i=0; i<N; ++i) {
        if (S[i] == '-') hy ++;
        else hy = 0;
        if (hy >= 3 && __builtin_popcount(hy+1) == 1 &&
            0 <= i-hy && S[i-hy] == 'o' &&
            i+1 < N && S[i+1] == 'o') {
                return "O";
        }
    }
    return "X";
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        int N; string S;
        cin >> N >> S;
        cout << solve(N, S) << endl;        
    }
    return 0;
}