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 PYTHON3):

Solution:
# DEFINING SOME GOOD STUFF
import sys
from math import *
import threading
from itertools import count
from pprint import pprint
from collections import defaultdict

'''
    intialise defaultdict by any kind of value by default you want to take ( int -> 0 | list -> [] )
'''
from heapq import heapify, heappop, heappush

sys.setrecursionlimit(300000)
# threading.stack_size(10**8)
'''
-> if you are increasing recursionlimit then remember submitting using python3 rather pypy3
-> sometimes increasing stack size don't work locally but it will work on CF
'''

mod = 10 ** 9+7
inf = 10 ** 15
decision = ['NO', 'YES']
yes = 'YES'
no = 'NO'

# ------------------------------FASTIO----------------------------
import os

from io import BytesIO, IOBase

BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n")+(not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")


# _______________________________________________________________#

def npr(n, r):
    return (factorial(n)%mod) // (factorial(n-r)%mod) if n >= r else 0


def ncr(n, r):
    return (factorial(n)%mod) // ((factorial(r)%mod) * (factorial(n-r)%mod)) if n >= r else 0


def lower_bound(li, num):
    answer = -1
    start = 0
    end = len(li)-1

    while (start <= end):
        middle = (end+start) // 2
        if li[middle] >= num:
            answer = middle
            end = middle-1
        else:
            start = middle+1
    return answer  # min index where x is not less than num


def upper_bound(li, num):
    answer = -1
    start = 0
    end = len(li)-1

    while (start <= end):
        middle = (end+start) // 2

        if li[middle] <= num:
            answer = middle
            start = middle+1

        else:
            end = middle-1
    return answer  # max index where x is not greater than num


def abs(x):
    return x if x >= 0 else -x


def binary_search(li, val):
    # print(lb, ub, li)
    ans = -1
    lb = 0
    ub = len(li)-1
    while (lb <= ub):
        mid = (lb+ub) // 2
        # print('mid is',mid, li[mid])
        if li[mid] > val:
            ub = mid-1
        elif val > li[mid]:
            lb = mid+1
        else:
            ans = mid  # return index
            break
    return ans


def kadane(x):  # maximum sum contiguous subarray
    sum_so_far = 0
    current_sum = 0
    for i in x:
        current_sum += i
        if current_sum < 0:
            current_sum = 0
        else:
            sum_so_far = max(sum_so_far, current_sum)
    return sum_so_far


def pref(li):
    pref_sum = [0]
    for i in li:
        pref_sum.append(pref_sum[-1]+i)
    return pref_sum


def SieveOfEratosthenes(n):
    prime = [{1, i} for i in range(n+1)]
    p = 2
    while (p <= n):
        for i in range(p * 2, n+1, p):
            prime[i].add(p)
        p += 1
    return prime


def primefactors(n):
    factors = []
    while (n % 2 == 0):
        factors.append(2)
        n //= 2
    for i in range(3, int(sqrt(n))+1, 2):  # only odd factors left
        while n % i == 0:
            factors.append(i)
            n //= i
    if n > 2:  # incase of prime
        factors.append(n)
    return factors


def prod(li):
    ans = 1
    for i in li:
        ans *= i
    return ans


def sumk(a, b):
    print('called for', a, b)
    ans = a * (a+1) // 2
    ans -= b * (b+1) // 2
    return ans

def sumi(n):
    ans = 0
    if len(n) > 1:
        for x in n:
            ans += int(x)
        return ans
    else:
        return int(n)

# _______________________________________________________________#


# def main():
karmanya = int(input())
# karmanya = 1
# divisors = SieveOfEratosthenes(200010)
# print(divisors)
while karmanya != 0:
    karmanya -= 1
    n = int(input())
    # n,m,x= map(int, input().split())
    # n,k= map(int, input().split())
    # a = [int(x) for x in input()]
    # a = list(map(int, input().split()))
    # b = list(map(int, input().split()))
    # c = list(map(int, input().split()))
    # d = defaultdict(int)
    s = list(input())
    ss= [0]
    f = 1
    # print(s)
    for i in s:
        # print(i, ss)
        # print(i in ss, s[-1])
        if i == ss[-1]:
            continue
        if i in ss:
            f = 0
            break
        else:
            ss.append(i)
        # print(f)
    print(decision[f])














































































































# t = threading.Thread(target=main)
# t.start()
# t.join()