#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, d;
  cin >> n >> d;
  int cd = d;
  string str;
  cin >> str;
  for (int i = 0; i < str.length(); i++) {
    int best = -1;
    char letter = str[i];
    for (unsigned char a = str[i], b = str[i]; a >= 'a' or b <= 'z'; a--, b++) {
      if (a >= 'a' and str[i] - a <= d and str[i] - a > best) {
        best = str[i] - a;
        letter = a;
      }
      if (b <= 'z' and b - str[i] <= d and b - str[i] > best) {
        best = b - str[i];
        letter = b;
      }
    }
    d -= best;
  }
  if (d == 0) {
    d = cd;
    for (int i = 0; i < str.length(); i++) {
      int best = -1;
      char letter = str[i];
      for (unsigned char a = str[i], b = str[i]; a >= 'a' or b <= 'z';
           a--, b++) {
        if (a >= 'a' and str[i] - a <= d and str[i] - a > best) {
          best = str[i] - a;
          letter = a;
        }
        if (b <= 'z' and b - str[i] <= d and b - str[i] > best) {
          best = b - str[i];
          letter = b;
        }
      }
      cout << letter;
      d -= best;
    }
  } else {
    cout << -1;
  }
  return 0;
}
