#include <bits/stdc++.h>
using namespace std;
int main() {
  char s[100000 + 7];
  int n, k;
  while (3 == scanf("%d %d %s", &n, &k, s)) {
    int d, r;
    string ans;
    for (int i = 0; i < n; i++) {
      if (k == 0) {
        ans += s[i];
        continue;
      }
      if (s[i] <= 109) {
        r = 122 - s[i];
        if (k >= r) {
          ans += 'z';
          k -= 'z' - s[i];
        } else {
          ans += s[i] + k;
          k = 0;
        }
      } else {
        r = s[i] - 97;
        if (k >= r) {
          ans += 'a';
          k -= s[i] - 'a';
        } else {
          ans += s[i] - k;
          k = 0;
        }
      }
    }
    if (!k)
      cout << ans << endl;
    else
      printf("-1\n");
  }
  return 0;
}
