#include <bits/stdc++.h>
using namespace std;
vector<string> v, vf;
int mini = 1e9;
int main() {
  int n, k;
  string t, myans;
  cin >> n >> k >> t;
  k--;
  if (!k) {
    cout << t;
    return 0;
  }
  for (int i = 0; i < n; ++i) {
    string ans = "";
    for (int j = i; j < n; ++j) {
      ans += t[j];
      v.push_back(ans);
    }
  }
  for (int i = 0; i < v.size(); ++i) {
    string nw = t + v[i];
    int cnt = 0;
    for (int j = 0; j < nw.size(); ++j) {
      string nwans;
      for (int k = j; k < nw.size(); ++k) {
        nwans += nw[k];
        if (nwans == t) {
          cnt++;
          break;
        }
      }
    }
    if (cnt == 2) {
      vf.push_back(nw);
    }
  }
  for (int i = 0; i < vf.size(); ++i) {
    if (vf.size() < mini) {
      mini = vf[i].size();
      myans = vf[i];
    }
  }
  string add = "";
  for (int i = n; i < myans.size(); ++i) {
    add += myans[i];
  }
  for (int i = 0; i < k - 1; ++i) {
    myans += add;
  }
  cout << myans;
  return 0;
}
