func_code_string: #include <bits/stdc++.h>   using namespace std;   void solve();   string conc(long long int a, long long int b) {     return to_string(a) +  |  + to_string(b);   }   long long int rev(long long int x) {     long long int ans = 0;     while (x != 0) {       ans = ans * 10 + (x % 10);       x /= 10;     }     return ans;   }   long long int numdig(long long int x) {     long long int ans = 0;     while (x != 0) {       ans++;       x /= 10;     }     return ans;   }   void printvec(vector<long long int> &v) {     for (long long int i = 0; i < v.size(); i++) cout << v[i] <<    ;     cout <<   n ;   }   void printmat(vector<vector<long long int>> &mat) {     for (long long int i = 0; i < mat.size(); i++) {       for (long long int j = 0; j < mat[0].size(); j++) cout << mat[i][j] <<    ;       cout <<   n ;     }   }   void solve() {     long long int n, k;     cin >> n >> k;     string s;     cin >> s;     vector<long long int> f(26, 0);     vector<pair<char, long long int>> v;     long long int vsize = 0;     for (auto c : s) f[c -  a ]++;     for (long long int i = 0; i < 26; i++) {       if (f[i] > 0) {         v.push_back({ a  + i, f[i]});         vsize++;       }     }     if (v[0].second < k) {       long long int count = 0;       for (long long int i = 0; i < vsize; i++) {         count += v[i].second;         if (count >= k) {           cout << v[i].first <<   n ;           return;         }       }       return;     }     string init =   ;     init = init + v[0].first;     vector<string> words(k, init);     v[0].second -= k;     for (long long int i = 0; i < vsize; i++) {       if (i == vsize - 1) {         long long int j = 0;         long long int c = 0;         while (j < k && words[j] == words[0]) j++;         while (v[i].second--) {           words[c] += v[i].first;           c = (c + 1) % j;         }       } else {         while (v[i].second--) {           words[0] += v[i].first;         }       }     }     sort(words.begin(), words.end());     cout << words[k - 1] <<   n ;   }   int main(void) {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     long long int t;     t = 1;     cin >> t;     while (t--) solve();     return 0;   }   