#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  int n, k;
  string s;
  cin >> n >> k;
  cin >> s;
  stringstream ss;
  for (int i = 0; i < s.length(); ++i) {
    int m1 = abs('a' - s[i]);
    int m2 = abs('z' - s[i]);
    int mx = max(m1, m2);
    if (k >= mx) {
      k -= mx;
      if (m1 > m2)
        ss << 'a';
      else
        ss << 'z';
    } else {
      char left = s[i] - k;
      if ('a' <= left) {
        ss << left;
        k = 0;
        continue;
      }
      char right = s[i] + k;
      ss << right;
      k = 0;
    }
  }
  if (k == 0) {
    cout << ss.str() << "\n";
  } else {
    cout << "-1\n";
  }
  return 0;
}
