#include <bits/stdc++.h>
using namespace std;
char s[100000 + 10], ans[100000 + 10];
int main() {
  int n, k;
  cin >> n >> k;
  scanf("%s", s);
  for (int i = 0; i < n; i++) {
    if (k == 0) {
      ans[i] = s[i];
      continue;
    }
    int dz = abs(s[i] - 'z');
    int da = abs(s[i] - 'a');
    if (k >= max(dz, da)) {
      if (dz > da) {
        ans[i] = 'z';
      } else {
        ans[i] = 'a';
      }
      k -= max(dz, da);
      continue;
    } else {
      if (s[i] + k <= 'z') {
        ans[i] = char(s[i] + k);
        k = 0;
        continue;
      } else {
        ans[i] = char(s[i] - k);
        k = 0;
        continue;
      }
    }
  }
  if (k > 0) {
    cout << -1 << endl;
    return 0;
  }
  printf("%s", ans);
}
