#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007, INF = mod * mod * 3LL;
int main() {
  cin.tie(0);
  cout.tie(0);
  ios::sync_with_stdio(false);
  string s;
  int n, k;
  cin >> n >> k >> s;
  string t = s;
  reverse((t).begin(), (t).end());
  s += t;
  string u = s.substr(0, n);
  for (int i = 1; i <= n; i++) u = min(u, s.substr(i, n));
  int x = 1;
  while (x < u.length() && u[0] == u[x]) x++;
  int y = x;
  k--;
  if (k > 17)
    y = n;
  else
    y <<= k;
  string ans = "";
  while (ans.length() < n && k > 0) y--, ans += u[0];
  ans += u.substr(x, n - ans.length());
  cout << ans << endl;
  return 0;
}
