Problem: Polycarp has 26 tasks. Each task is designated by a capital letter of the Latin alphabet.

The teacher asked Polycarp to solve tasks in the following way: if Polycarp began to solve some task, then he must solve it to the end, without being distracted by another task. After switching to another task, Polycarp cannot return to the previous task.

Polycarp can only solve one task during the day. Every day he wrote down what task he solved. Now the teacher wants to know if Polycarp followed his advice.

For example, if Polycarp solved tasks in the following order: "DDBBCCCBBEZ", then the teacher will see that on the third day Polycarp began to solve the task 'B', then on the fifth day he got distracted and began to solve the task 'C', on the eighth day Polycarp returned to the task 'B'. Other examples of when the teacher is suspicious: "BAB", "AABBCCDDEEBZZ" and "AAAAZAAAAA".

If Polycarp solved the tasks as follows: "FFGZZZY", then the teacher cannot have any suspicions. Please note that Polycarp is not obligated to solve all tasks. Other examples of when the teacher doesn't have any suspicious: "BA", "AFFFCC" and "YYYYY".

Help Polycarp find out if his teacher might be suspicious.

Input

The first line contains an integer t (1 ≤ t ≤ 1000). Then t test cases follow.

The first line of each test case contains one integer n (1 ≤ n ≤ 50) — the number of days during which Polycarp solved tasks.

The second line contains a string of length n, consisting of uppercase Latin letters, which is the order in which Polycarp solved the tasks.

Output

For each test case output: 

  * "YES", if the teacher cannot be suspicious; 
  * "NO", otherwise. 



You may print every letter in any case you want (so, for example, the strings yEs, yes, Yes and YES are all recognized as positive answer).

Example

Input


5
3
ABA
11
DDBBCCCBBEZ
7
FFGZZZY
1
Z
2
AB


Output


NO
NO
YES
YES
YES

Solution (in JAVA):

Solution:
import java.io.*;
import java.util.*;

public class Main {
    static OutputWriter out;
    static int MAX = 0;

    public static void main(String[] args) throws Exception {
        MyScanner in = new MyScanner(System.in);
        out = new OutputWriter(System.out);
        int t = in.nextInt();
        for (int j = 0 ; j<t;j++) {
            int n = in.nextInt();
            String s = in.nextLine();
            int[] nums = new int[26];
            nums[s.charAt(0) - 'A']++;
            boolean ans = true;
            for (int i = 1; i < n; i++) {
                if (s.charAt(i) != s.charAt(i - 1) && nums[s.charAt(i) - 'A'] > 0) {
                    ans = false;
                    break;
                }
                nums[s.charAt(i) - 'A']++;
            }
            out.printLine(ans ? "YES" : "NO");
        }
        out.flush();
    }

    static long[] reverse(long a[], int n) {
        long[] b = new long[n];
        int j = n;
        for (int i = 0; i < n; i++) {
            b[j - 1] = a[i];
            j = j - 1;
        }
        return b;
    }

    static void MergeSort(long[] a, int p, int r) {
        if (p < r) {
            int q = (r + p) / 2;
            MergeSort(a, p, q);
            MergeSort(a, q + 1, r);
            Merge(a, p, q, r);
        }
    }

    static void Merge(long[] a, int p, int q, int r) {
        int n1 = q - p + 1;
        int n2 = r - q;
        long[] R = new long[n1 + 1];
        long[] L = new long[n2 + 1];

        for (int i = 0; i < n1; i++) {
            R[i] = a[p + i];
        }
        R[n1] = Long.MAX_VALUE;
        for (int i = 0; i < n2; i++) {
            L[i] = a[q + i + 1];
        }
        L[n2] = Long.MAX_VALUE;
        int n = a.length;
        int j = 0;
        int k = 0;
        for (int i = p; i <= r; i++) {
            if (L[j] <= R[k]) {
                a[i] = L[j];
                j++;
            } else {
                a[i] = R[k];
                k++;
            }


        }
    }
}

class Graph {


    int n;
    ArrayList<Integer>[] adjList;

    public Graph(int n) {
        this.n = n;
        adjList = new ArrayList[n];
        for (int i = 0; i < n; i++)
            adjList[i] = new ArrayList<>();
    }

}

class pair implements Comparable {

    int key;
    int value;

    public pair(Object key, Object value) {

        this.key = (int) key;
        this.value = (int) value;

    }

    @Override
    public int compareTo(Object o) {
        pair temp = (pair) o;
        return key - temp.key;
    }
}

class MyScanner {

    StringTokenizer st;
    BufferedReader br;

    public MyScanner(InputStream s) {
        br = new BufferedReader(new InputStreamReader(s));
    }

    public MyScanner(FileReader f) {
        br = new BufferedReader(f);
    }

    public String next() throws IOException {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine());
        return st.nextToken();
    }

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

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

    public String nextLine() throws IOException {
        return br.readLine();
    }

    public double nextDouble() throws IOException {
        String x = next();
        StringBuilder sb = new StringBuilder("0");
        double res = 0, f = 1;
        boolean dec = false, neg = false;
        int start = 0;
        if (x.charAt(0) == '-') {
            neg = true;
            start++;
        }
        for (int i = start; i < x.length(); i++)
            if (x.charAt(i) == '.') {
                res = Long.parseLong(sb.toString());
                sb = new StringBuilder("0");
                dec = true;
            } else {
                sb.append(x.charAt(i));
                if (dec)
                    f *= 10;
            }
        res += Long.parseLong(sb.toString()) / f;
        return res * (neg ? -1 : 1);
    }

    public boolean ready() throws IOException {
        return br.ready();
    }

    public boolean nextEmpty() throws IOException {
        String s = nextLine();
        st = new StringTokenizer(s);
        return s.isEmpty();
    }
}

class OutputWriter {
    private final PrintWriter writer;

    public OutputWriter(OutputStream outputStream) {
        writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
    }

    public OutputWriter(Writer writer) {
        this.writer = new PrintWriter(writer);
    }

    public void print(Object... objects) {
        for (int i = 0; i < objects.length; i++) {
            if (i != 0)
                writer.print(' ');
            writer.print(objects[i]);
        }
    }


    public void printLine(Object... objects) {
        print(objects);
        writer.println();
    }

    public void close() {
        writer.close();
    }

    public void flush() {
        writer.flush();
    }

}