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.math.*;
import java.util.*;
import java.io.*;
 
 
 
public class main
{
  static Map<String,Integer> map=new HashMap<>();
    public static void main(String[] args)
    {
        InputReader in = new InputReader(System.in);
        PrintWriter pw = new PrintWriter(System.out);
         final int mod=1000000007;
        int test_case =in.nextInt();
                    StringBuilder sb=new StringBuilder();
      for(int t1=0;t1<test_case;t1++)
      {
          //System.out.println("hello world");
        int n=in.nextInt();
       String s=in.nextLine();
       Set<Character> set=new HashSet<Character>();
       set.add(s.charAt(0));
       String ans="YES";
       for(int i=1;i<s.length();i++)
       {
           if(s.charAt(i)!=s.charAt(i-1)&&set.contains(s.charAt(i)))
           {
               ans="NO";
               
               break;
           }
               set.add(s.charAt(i));
          
          
           
       }
        System.out.println(ans);
      }
    
 
 
        pw.flush();
        pw.close();
    }
    
    
    static int factorial(int n,int mod)
    {
        long res = 1;
        for (int i=2; i<=n; i++)
            res=((res%mod)*(i%mod))%mod;
        return (int)res;
    }
    
 
 
    
    static int length(long l)
    {
        int c=0;
        while(l>0)
        {
            c++;
            l/=2;
        }
        
        return c;
    }
 
    
    static int CeilIndex(int A[], int l, int r, int key) 
    { 
        while (r - l > 1) { 
            int m = l + (r - l) / 2; 
            if (A[m] <= key) 
                r = m; 
            else
                l = m; 
        } 
  
        return r; 
    } 
    static int LongestIncreasingSubsequenceLength(int A[], int size) 
    { 
        // Add boundary case, when array size is one 
  
        int[] tailTable = new int[size]; 
        int len; // always points empty slot 
  
        tailTable[0] = A[0]; 
        len = 1; 
        for (int i = 1; i < size; i++) { 
            if (A[i] > tailTable[0]) 
 
                tailTable[0] = A[i]; 
  
            else if (A[i] <= tailTable[len - 1]) 
 
                tailTable[len++] = A[i]; 
  
            else
 
                tailTable[CeilIndex(tailTable, -1, len - 1, A[i])] = A[i]; 
        } 
  
        return len; 
    }
    
 
    
    static int[] next(int arr[], int n) { 
 
        Stack<Integer> S = new Stack<>(); 
  
        int[] next=new int[n];
 
        for (int i = n-1; i >= 0; i--) { 
 
            while (!S.empty() && arr[S.peek()] <= arr[i]) { 
                S.pop(); 
 
            } 
            if (S.empty()) { 
                next[i]=-1;
            } 
            else 
            { 
 
                next[i]=S.peek(); 
            } 
            S.push(i); 
        } 
        return next;
    }
    static int[] back(int arr[], int n) { 
 
        Stack<Integer> S = new Stack<>(); 
  
        int[] back=new int[n];
 
        for (int i = 0; i < n; i++) { 
 
            while (!S.empty() && arr[S.peek()] < arr[i]) { 
                S.pop(); 
            } 
            if (S.empty()) { 
                back[i]=-1;
            } 
            else 
            { 
                back[i]=S.peek(); 
            } 
            S.push(i); 
        } 
        
        return back;
    }
 
    
    
 
    static class InputReader
    {
 
        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        private SpaceCharFilter filter;
 
        public InputReader(InputStream stream)
        {
            this.stream = stream;
        }
 
        public int snext()
        {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars)
            {
                curChar = 0;
                try
                {
                    snumChars = stream.read(buf);
                }
                catch (IOException e)
                {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
 
        public int nextInt()
        {
            int c = snext();
            while (isSpaceChar(c))
            {
                c = snext();
            }
            int sgn = 1;
            if (c == '-')
            {
                sgn = -1;
                c = snext();
            }
            int res = 0;
            do
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
 
        public long nextLong()
        {
            int c = snext();
            while (isSpaceChar(c))
            {
                c = snext();
            }
            int sgn = 1;
            if (c == '-')
            {
                sgn = -1;
                c = snext();
            }
            long res = 0;
            do
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
 
        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;
        }
 
        public String readString()
        {
            int c = snext();
            while (isSpaceChar(c))
            {
                c = snext();
            }
            StringBuilder res = new StringBuilder();
            do
            {
                res.appendCodePoint(c);
                c = snext();
            } while (!isSpaceChar(c));
            return res.toString();
        }
 
        public String nextLine()
        {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            StringBuilder res = new StringBuilder();
            do
            {
                res.appendCodePoint(c);
                c = snext();
            } while (!isEndOfLine(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;
        }
 
        private boolean isEndOfLine(int c)
        {
            return c == '\n' || c == '\r' || c == -1;
        }
 
        public interface SpaceCharFilter
        {
            public boolean isSpaceChar(int ch);
        }
    }
 
    public static long mod = 1000000007;
    public static int d;
    public static int p;
    public static int q;
 
    public static int[] suffle(int[] a,Random gen)
    {
        int n = a.length;
        for(int i=0;i<n;i++)
        {
            int ind = gen.nextInt(n-i)+i;
            int temp = a[ind];
            a[ind] = a[i];
            a[i] = temp;
        }
        return a;
    }
 
    public static void swap(int a, int b){
        int temp = a;
        a = b;
        b = temp;
    }
 
    public static HashSet<Integer> primeFactorization(int n)
    {
        HashSet<Integer> a =new HashSet<Integer>();
        for(int i=2;i*i<=n;i++)
        {
            while(n%i==0)
            {
                a.add(i);
                n/=i;
            }
        }
        if(n!=1)
            a.add(n);
        return a;
    }
 
    public static void sieve(boolean[] isPrime,int n)
    {
        for(int i=1;i<n;i++)
            isPrime[i] = true;
 
        isPrime[0] = false;
        isPrime[1] = false;
 
        for(int i=2;i*i<n;i++)
        {
            if(isPrime[i] == true)
            {
                for(int j=(2*i);j<n;j+=i)
                    isPrime[j] = false;
            }
        }
    }
 
    public static int GCD(int a,int b)
    {
        if(b==0)
            return a;
        else
            return GCD(b,a%b);
    }
 
    public static long GCD(long a,long b)
    {
        if(b==0)
            return a;
        else
            return GCD(b,a%b);
    }
 
    public static void extendedEuclid(int A,int B)
    {
        if(B==0)
        {
            d = A;
            p = 1 ;
            q = 0;
        }
        else
        {
            extendedEuclid(B, A%B);
            int temp = p;
            p = q;
            q = temp - (A/B)*q;
        }
    }
 
    public static long LCM(long a,long b)
    {
        return (a*b)/GCD(a,b);
    }
 
    public static int LCM(int a,int b)
    {
        return (a*b)/GCD(a,b);
    }
 
    public static int binaryExponentiation(int x,int n)
    {
        int result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=result * x;
            x=x*x;
            n=n/2;
        }
        return result;
    }
    int binarySearch(int arr[], int l, int r, int x) 
    { 
        if (r >= l) { 
            int mid = l + (r - l) / 2; 
  
 
            if (arr[mid] == x) 
                return mid; 
  
 
            if (arr[mid] > x) 
                return binarySearch(arr, l, mid - 1, x); 
  
 
            return binarySearch(arr, mid + 1, r, x); 
        } 
  
 
        return -1; 
    } 
  
 
    public static long binaryExponentiation(long x,long n)
    {
        long result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=result * x;
            x=x*x;
            n=n/2;
        }
        return result;
    }
 
    public static int modularExponentiation(int x,int n,int M)
    {
        int result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=(result * x)%M;
            x=(x*x)%M;
            n=n/2;
        }
        return result;
    }
 
    public static long modularExponentiation(long x,long n,long M)
    {
        long result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=(result * x)%M;
            x=(x*x)%M;
            n=n/2;
        }
        return result;
    }
 
    public static int modInverse(int A,int M)
    {
        return modularExponentiation(A,M-2,M);
    }
 
    public static long modInverse(long A,long M)
    {
        return modularExponentiation(A,M-2,M);
    }
 
    public static boolean isPrime(int n)
    {
 
        if (n <= 1)  return false;
        if (n <= 3)  return true;
 
        if (n%2 == 0 || n%3 == 0)
            return false;
 
        for (int i=5; i*i<=n; i=i+6)
        {
            if (n%i == 0 || n%(i+2) == 0)
                return false;
        }
 
        return true;
    }
    static class Pair
    {
        long  x;
        int  y;
    }
 
    static class pair implements Comparable<pair>
    {
        Integer x, y;
        pair(int x,int y)
        {
            this.x=x;
            this.y=y;
        }
 
        public int compareTo(pair o) {
            int result = x.compareTo(o.x);
            if(result==0)
                result = y.compareTo(o.y);
 
            return result;
        }
 
        public String toString()
        {
            return x+" "+y;
        }
 
        public boolean equals(Object o)
        {
            if (o instanceof pair)
            {
                pair p = (pair)o;
                return (Math.abs(p.x-x)==0 && Math.abs(p.y-y)==0);
            }
            return false;
        }
 
        public int hashCode()
        {
            return new Long(x).hashCode()*31 + new Long(y).hashCode();
        }
    }
}