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:
#include<bits/stdc++.h>
//#include<ext/pb_ds/assoc_container.hpp>
//#include<ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/trie_policy.hpp>
//using namespace __gnu_pbds;
using namespace std;
#define ll 				long long int
#define ld				long double
#define mod             1000000007
#define inf             1e18
#define endl			"\n"
#define pb 				push_back
#define vi              vector<ll>
#define vs				vector<string>
#define pii             pair<ll,ll>
#define ump				unordered_map
#define mp 				make_pair
#define pq_max          priority_queue<ll>
#define pq_min          priority_queue<ll,vi,greater<ll> >
#define all(n) 			n.begin(),n.end()
#define ff 				first
#define ss 				second
#define mid(l,r)        (l+(r-l)/2)
#define bitc(n) 		__builtin_popcount(n)
#define loop(i,a,b) 	for(int i=(a);i<=(b);i++)
#define looprev(i,a,b) 	for(int i=(a);i>=(b);i--)
#define iter(container, it) for(__typeof(container.begin()) it = container.begin(); it != container.end(); it++)
#define log(args...) 	{ string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }
#define logarr(arr,a,b)	for(int z=(a);z<=(b);z++) cout<<(arr[z])<<" ";cout<<endl;	
template <typename T> T gcd(T a, T b){if(a%b) return gcd(b,a%b);return b;}
template <typename T> T lcm(T a, T b){return (a*(b/gcd(a,b)));}
vs tokenizer(string str,char ch) {std::istringstream var((str)); vs v; string t; while(getline((var), t, (ch))) {v.pb(t);} return v;}
void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
    cout << *it << " = " << a << endl;
    err(++it, args...);
}
//typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> pbds;
//typedef trie<string,null_type,trie_string_access_traits<>,pat_trie_tag,trie_prefix_search_node_update> pbtrie;
void file_i_o()
{
    ios_base::sync_with_stdio(0); 
    cin.tie(0); 
    cout.tie(0);
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}
int main(int argc, char const *argv[]) {
    clock_t begin = clock();
    file_i_o();
    // Write your code here....
    int t;
    cin>>t;
    while(t--){
        int n;
        cin>>n;
        set<char> ts;
        string s;
        cin>>s;
        int fl=0;
        ts.insert(s[0]);
        for(int i=1;i<n;i++){
            if(s[i]==s[i-1]){
                continue;
            }else{
                if(ts.find(s[i])==ts.end()){
                    ts.insert(s[i]);
                }else{
                    cout<<"NO\n";
                    fl=1;
                    break;
                }
            }
        }
        if(fl!=1){
            cout<<"YES\n";
        }
    }                   
    #ifndef ONLINE_JUDGE         
      clock_t end = clock();
      cout<<"\n\nExecuted In: "<<double(end - begin) / CLOCKS_PER_SEC*1000<<" ms";
    #endif 
    return 0;
}