#include <bits/stdc++.h>
using namespace std;
int main(int argc, char* argv[]) {
  int n, d;
  scanf("%d %d", &n, &d);
  static char buff[300500];
  scanf("%s", buff);
  char middle_char = 'a' + 11;
  int now;
  for (int i = 0; buff[i] && d > 0; i++) {
    if (buff[i] <= middle_char) {
      now = min(d, int('z' - buff[i]));
      buff[i] += now;
    } else {
      now = min(d, int(buff[i] - 'a'));
      buff[i] -= now;
    }
    d -= now;
  }
  if (d > 0)
    cout << "-1" << endl;
  else
    cout << buff << endl;
  return 0;
}
