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.*;
import java.math.*;
import java.lang.*;

public class Main implements Runnable {
    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        private BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1)
                throw new InputMismatchException();

            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }

                if (numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

        public int nextInt() {
            int c = read();

            while (isSpaceChar(c))
                c = read();

            int sgn = 1;

            if (c == '-') {
                sgn = -1;
                c = read();
            }

            int res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));

            return res * sgn;
        }

        public long nextLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;

            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c)) {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));

            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next() {
            return readString();
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }

    public static void main(String args[]) throws Exception {
        new Thread(null, new Main(), "Main", 1 << 27).start();
    }

    static class Pair {
        int f;
        int s;
        int p;
        PrintWriter w;

        // int t;

        Pair(int f, int s) {
            // Pair(int f,int s, PrintWriter w){
            this.f = f;
            this.s = s;
            // this.p = p;
            // this.w = w;
            // this.t = t;

        }

        public static Comparator<Pair> wc = new Comparator<Pair>() {
            public int compare(Pair e1,Pair e2){

                // 1 for swap
                if(Math.abs(e1.f)-Math.abs(e2.f)!=0){
                // e1.w.println("**"+e1.f+" "+e2.f);
                    return (Math.abs(e1.f)-Math.abs(e2.f));
                }
                else{
                // e1.w.println("##"+e1.f+" "+e2.f);
                    return (Math.abs(e1.s)-Math.abs(e2.s));
                }

        
            }
        };
    }

    public Integer[] sort(Integer[] a) {
        Arrays.sort(a);
        return a;
    }

    public Long[] sort(Long[] a) {
        Arrays.sort(a);
        return a;
    }

    public static ArrayList<Integer> sieve(int N) {
        int i, j, flag;

        ArrayList<Integer> p = new ArrayList<Integer>();

        for (i = 1; i < N; i++) {

            if (i == 1 || i == 0)
                continue;

            flag = 1;

            for (j = 2; j <= i / 2; ++j) {
                if (i % j == 0) {
                    flag = 0;
                    break;
                }
            }
            if (flag == 1) {
                p.add(i);
            }
        }
        return p;
    }

    public static long gcd(long a, long b) {
        if (b == 0)
            return a;
        else
            return gcd(b, a % b);
    }

    public static int gcd(int a, int b) {
        if (b == 0)
            return a;
        else
            return gcd(b, a % b);
    }

    //// recursive dfs
    public static int dfs(int s, ArrayList<Integer>[] g, long[] dist, boolean[] v, PrintWriter w, int p) {
        v[s] = true;
        int ans = 1;
        // int n = dist.length - 1;
        int t = g[s].size();
        // int max = 1;
        for (int i = 0; i < t; i++) {
            int x = g[s].get(i);
            if (!v[x]) {
                // dist[x] = dist[s] + 1;
                ans = Math.min(ans, dfs(x, g, dist, v, w, s));
            } else if (x != p) {
                // w.println("* " + s + " " + x + " " + p);
                ans = 0;
            }
        }
        // max = Math.max(max,(n-p));
        return ans;
    }

    //// iterative BFS
    public static int bfs(int s, ArrayList<Integer>[] g, long[] dist, boolean[] b, PrintWriter w, int p) {
        b[s] = true;
        int siz = 1;
        // dist--;
        Queue<Integer> q = new LinkedList<>();
        q.add(s);
        while (q.size() != 0) {
            int i = q.poll();
            Iterator<Integer> it = g[i].listIterator();
            int z = 0;
            while (it.hasNext()) {
                z = it.next();
                if (!b[z]) {
                    b[z] = true;
                    // dist--;
                    dist[z] = dist[i] + 1;
                    // siz++;
                    q.add(z);
                } else if (z != p) {
                    siz = 0;
                }
            }

        }
        return siz;
    }

    public static int lower(int a[], int x) { // x is the target value or key
        int l = -1, r = a.length;
        while (l + 1 < r) {
            int m = (l + r) >>> 1;
            if (a[m] >= x)
                r = m;
            else
                l = m;
        }
        return r;
    }

    public static int upper(int a[], int x) {// x is the key or target value
        int l = -1, r = a.length;
        while (l + 1 < r) {
            int m = (l + r) >>> 1;
            if (a[m] <= x)
                l = m;
            else
                r = m;
        }
        return l + 1;
    }

    public static int lower(ArrayList<Integer> a, int x) { // x is the target value or key
        int l = -1, r = a.size();
        while (l + 1 < r) {
            int m = (l + r) >>> 1;
            if (a.get(m) >= x)
                r = m;
            else
                l = m;
        }
        return r;
    }

    public static int upper(ArrayList<Integer> a, int x) {// x is the key or target value
        int l = -1, r = a.size();
        while (l + 1 < r) {
            int m = (l + r) >>> 1;
            if (a.get(m) <= x)
                l = m;
            else
                r = m;
        }
        return l + 1;
    }

    public static long power(long x, long y, long m) {
        if (y == 0)
            return 1;

        long p = power(x, y / 2, m) % m;
        p = (p * p) % m;

        if (y % 2 == 0)
            return p;
        else
            return (x * p) % m;
    }

    public void yesOrNo(boolean f) {
        if (f) {
            w.println("YES");
        } else {
            w.println("NO");
        }
    }

    // Arrays.sort(rooms, (room1, room2) -> room1[1] == room2[1] ? room1[0]-room2[0]
    // : room2[1]-room1[1]);
    // Arrays.sort(A, (a, b) -> Integer.compare(a[0] , b[0]));
    //////////////////////////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////////////
    // code here
    int oo = (int) 1e9;
    int[] parent;
    int[] dist;
    int[] height;
    boolean[] vis;
    // ArrayList<Integer>[] g;
    // int[] col;
    // HashMap<Long, Boolean>[] dp;
    char[][] g;
    // boolean[][] v;
    // long[] a;
    // ArrayList<Integer[]> a;
    // int[][] ans;
    long[][][] dp;
    long mod;
    int n;
    int m;
    int k;
    long[][] pre;
    // StringBuilder[] a;
    // StringBuilder[] b;
    // StringBuilder ans;
    int[][] col;
    int[][] row;
    PrintWriter w = new PrintWriter(System.out);

    public void run() {

        InputReader sc = new InputReader(System.in);

        int defaultValue = 0;
        mod = 1000000007;

        int test = 1;
        test = sc.nextInt();
        while (test-- > 0) {
            n = sc.nextInt();
            char[] c = sc.next().toCharArray();
            int[] a = new int[26];
            a[c[0]-'A']++;
            boolean f = true;
            for(int i=1;i<n;i++){
                if(c[i]!=c[i-1]){
                    if(a[c[i]-'A']>0){
                        f = false;
                        break;
                    }
                    else{
                        a[c[i]-'A']++;
                    }
                }
                
            }
            yesOrNo(f);
            

        }

        w.flush();
        w.close();

    }

}