#include <bits/stdc++.h>
using namespace std;
int x[100001];
int y[100001];
int main() {
  int n, m;
  cin >> n >> m;
  string s;
  cin >> s;
  int col = 0;
  for (int i = 0; i < n; i++) {
    s[i] = s[i] - 'a' + 1;
    col += max(s[i] - 1, 26 - s[i]);
  }
  if (col < m) {
    cout << -1;
    return 0;
  } else {
    for (int i = 0; i < n; i++) {
      int l = max(s[i] - 1, 26 - s[i]);
      int r = min(l, m);
      if (r == l) {
        if (l == s[i] - 1)
          s[i] = s[i] - r + 'a' - 1;
        else
          s[i] = s[i] + r + 'a' - 1;
      } else if (r == m) {
        if (s[i] + m > 25) {
          s[i] = s[i] - r + 'a' - 1;
        } else
          s[i] = s[i] + r + 'a' - 1;
      }
      m -= r;
    }
  }
  cout << s << endl;
  return 0;
}
