#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 5, OO = 0x3f3f3f3f, MOD = 1000000007;
const double EPS = 0.000000001;
int main() {
  int n, k;
  cin >> n >> k;
  string s, ss = "";
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    if (k >= max(abs('a' - s[i]), abs('z' - s[i]))) {
      if (abs('a' - s[i]) > abs('z' - s[i]))
        ss += 'a';
      else
        ss += 'z';
      k -= max(abs('a' - s[i]), abs('z' - s[i]));
    } else {
      char c;
      if (s[i] + k <= 'z')
        c = s[i] + k;
      else if (s[i] - k >= 'a')
        c = s[i] - k;
      ss += c;
      k = 0;
    }
  }
  if (k)
    cout << -1;
  else
    cout << ss;
}
