import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int t = Integer.parseInt(br.readLine());
		PrintWriter pw = new PrintWriter(System.out);
		label:
		for (int i = 0; i < t; i++) {
			String[] sa = br.readLine().split(" ");
			String s = sa[1];
			if (s.indexOf("ooo") != -1
					|| s.indexOf("oo-") != -1
					|| s.indexOf("-oo") != -1
					|| s.indexOf("--o-") != -1
					|| s.indexOf("-o--") != -1
					|| s.indexOf("o-o") != -1
					) {
				pw.println("O");
			} else {
				int cnt = 0;
				for (int j = 0; j < s.length(); j++) {
					if (s.charAt(j) == 'o') {
						if (cnt % 2 == 1) {
							pw.println("O");
							continue label;
						}
						cnt = 0;
					} else if (s.charAt(j) == 'x') {
						cnt = 0;
					} else {
						cnt++;
					}
				}
				pw.println("X");
			}
		}
		br.close();
		pw.flush();
	}
}