import java.util.*;
import java.io.*;

public class Main {
	static final int mod = (int) 1e9 + 7;
	static final int DX[] = { -1, 0, 1, 0 }, DY[] = { 0, -1, 0, 1 };
	static final int[] DX8 = { -1, -1, -1, 0, 0, 1, 1, 1 }, DY8 = { -1, 0, 1, -1, 1, -1, 0, 1 };
	static final int INF = Integer.MAX_VALUE / 3;
	static final long LINF = Long.MAX_VALUE / 3;
	static final String nextLine = "\n";

	public static void main(String[] args) {
		FastScanner fs = new FastScanner(System.in);
		int t = fs.nextInt();
		for(int i=0;i<t;i++) {
			int n = fs.nextInt();
			String s = fs.next();
			char c[] = s.toCharArray();
			if(dfs(c,0))System.out.println("O");
			else System.out.println("X");
		}
	}
	
	static boolean check(char c[]) {
		int n = c.length;
		int cnt = 0;
		for(int i=0;i<n;i++) {
			if(c[i]=='o')cnt++;
			else cnt = 0;
			if(cnt>=3)return true;
		}
		return false;
	}
	
	static boolean dfs(char c[], int t) {
		int n = c.length;
		
		//終了チェック
		boolean go = false;
		for(int i=0;i<n;i++) {
			if(c[i]=='-') go = true;	
		}
		if(!go) {
			return check(c);
		}
		
		if(t%2==0) {//Oさんの番
			boolean ret = false;
			for(int i=0;i<n;i++) {
				if(c[i]=='-') {
					c[i]='o';
					ret |= dfs(c, t+1);
					c[i]='-';
				}
			}
			return ret;
		}
		else {//Xさんの番
			for(int i=0;i<n;i++) {
				if(c[i]=='-') {
					c[i]='x';
					if(!dfs(c, t+1)) {
						c[i]='-';
						return false;
					}
					c[i]='-';
				}
			}
			return true;
		}
	}

	//MOD culculations
	static long plus(long x, long y) {
		long res = (x + y) % mod;
		return res < 0 ? res + mod : res;
	}

	static long sub(long x, long y) {
		long res = (x - y) % mod;
		return res < 0 ? res + mod : res;
	}

	static long mul(long x, long y) {
		long res = (x * y) % mod;
		return res < 0 ? res + mod : res;
	}

	static long div(long x, long y) {
		long res = x * pow(y, mod - 2) % mod;
		return res < 0 ? res + mod : res;
	}

	static long pow(long x, long y) {
		if (y < 0)
			return 0;
		if (y == 0)
			return 1;
		if (y % 2 == 1)
			return (x * pow(x, y - 1)) % mod;
		long root = pow(x, y / 2);
		return root * root % mod;
	}
}

//高速なScanner
class FastScanner {
	private BufferedReader reader = null;
	private StringTokenizer tokenizer = null;

	public FastScanner(InputStream in) {
		reader = new BufferedReader(new InputStreamReader(in));
		tokenizer = null;
	}

	public String next() {
		if (tokenizer == null || !tokenizer.hasMoreTokens()) {
			try {
				tokenizer = new StringTokenizer(reader.readLine());
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		return tokenizer.nextToken();
	}

	public String nextLine() {
		if (tokenizer == null || !tokenizer.hasMoreTokens()) {
			try {
				return reader.readLine();
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		return tokenizer.nextToken("\n");
	}

	public long nextLong() {
		return Long.parseLong(next());
	}

	public int nextInt() {
		return Integer.parseInt(next());
	}

	public double nextDouble() {
		return Double.parseDouble(next());
	}

	public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = nextInt();
		return a;
	}

	public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nextLong();
		return a;
	}
}