#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  int ans = 0;
  for (int i = 0; i < n; i++) {
    int x = max(abs(s.at(i) - 'a'), abs(s.at(i) - 'z'));
    ans += x;
  }
  if (k > ans)
    cout << "-1" << endl;
  else if (k <= n) {
    int j = 0;
    while (k > 0) {
      if (s.at(j) + 1 <= 'z')
        cout << (char)(s.at(j) + 1);
      else
        cout << (char)(s.at(j) - 1);
      j++;
      k--;
    }
    for (; j < n; j++) cout << s.at(j);
  } else {
    for (int i = 0; i < n; i++) {
      int cur = k - (n - i - 1);
      char c = s.at(i);
      int x = abs(c - 'a');
      int y = abs('z' - c);
      if (x > y) {
        if (cur <= x) {
          cout << (char)(c - cur);
          for (int j = i + 1; j < n; j++) {
            if (s.at(j) + 1 <= 'z')
              cout << (char)(s.at(j) + 1);
            else
              cout << (char)(s.at(j) - 1);
          }
          break;
        } else {
          cout << (char)(c - x);
          k -= x;
        }
      } else {
        if (cur <= y) {
          cout << (char)(c + cur);
          for (int j = i + 1; j < n; j++) {
            if (s.at(j) + 1 <= 'z')
              cout << (char)(s.at(j) + 1);
            else
              cout << (char)(s.at(j) - 1);
          }
          break;
        } else {
          cout << (char)(c + y);
          k -= y;
        }
      }
    }
  }
  cout << endl;
  return 0;
}
