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 CPP):

Solution:
// Problem: A. Do Not Be Distracted!
// Contest: Codeforces - Codeforces Round #719 (Div. 3)
// URL: https://codeforces.com/contest/1520/problem/A
// Memory Limit: 256 MB
// Time Limit: 1000 ms

// Disclaimer: Don't copy my template, it may lead to plagiarism.
/* Author: Soumy Jain
   Handle: soumy_jain || soumyjain
   "Beautiful flowers too, eventually wither and fall. That's the fate of all living beings."
   "I hate perfection. To be perfect is to be unable to improve any furthur." - Mayuri Kurotsuchi | Bleach
   "I smile to show the pressure of heroes and to trick the fear inside of me."
   "Gravel may be gravel, but me? I'm the gravel that shatters diamonds."
   "If you were to write a story with me in the lead role, it would certainly be...a TRAGEDY." - Kaneki Ken | Tokyo
   Ghoul
*/
/******************************************************************************/
// clang-format off
#include <bits/stdc++.h>
#define ll        long long
#define ull       unsigned long long
#define SPEEDHACK ios_base::sync_with_stdio(false);cin.tie(NULL);
#define ff        first
#define ss        second
#define sz(v)     (ll)(v).size()
#define file      freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
#define MOD       1000000007      // 998244353
using namespace std;
/******************************************************************************/
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(ll x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(ull x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template<typename T, typename V>
void __print(const pair<T, V> &x) { cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}'; }
template<typename T>
void __print(const T &x) { int f = 0; cerr << '{'; for (auto &i : x) cerr << (f++ ? "," : ""), __print(i); cerr << "}"; }
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) { __print(t); if (sizeof...(v)) cerr << ", "; _print(v...); }
#ifndef ONLINE_JUDGE
#define dbg(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define dbg(x...)
#endif
// clang-format on

/***********************************MAIN***************************************/
// Are you ready to face the wrath of test cases? Good luck noob Soumy!

void work()
{
    ll n;
    cin >> n;
    string s;
    cin >> s;
    map<char, ll> M;
    for (int i = 0; i < n; i++)
    {
        if (M[s[i]] >= 1)
        {
            cout << "NO\n";
            return;
        }
        M[s[i]]++;
        while (i + 1 < n && s[i] == s[i + 1])
        {
            i++;
            M[s[i]]++;
        }
    }
    cout << "YES\n";
}

int main()
{
    SPEEDHACK
    // file
    ll t = 1;
    cin >> t;
    while (t--)
    {
        work();
    }
    return 0;
}