func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 1e5 + 5;   const int inf = 1e9;   char aa[maxn];   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     int t;     cin >> t;     while (t--) {       int n, k;       cin >> n >> k;       for (int i = 1; i <= n; i++) {         cin >> aa[i];       }       sort(aa + 1, aa + 1 + n);       if (aa[1] != aa[k])         cout << aa[k] << endl;       else {         int mark = 1;         if (aa[n] == aa[k + 1]) mark = 0;         if (mark == 0) {           for (int i = 1; i <= n; i += k) cout << aa[i];           cout << endl;         } else {           cout << aa[1];           for (int i = k + 1; i <= n; i++) cout << aa[i];           cout << endl;         }       }     }     return 0;   }   