#include <bits/stdc++.h>
using namespace std;
char input[100001];
char output[100001];
int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  scanf("%s", input);
  int diff;
  char c;
  bool f = true;
  for (int i = 0; i < n; i++) {
    if ('z' - input[i] >= input[i] - 'a') {
      diff = 'z' - input[i];
      c = 'z';
    } else {
      diff = input[i] - 'a';
      c = 'a';
    }
    if (k >= diff) {
      output[i] = c;
      k = k - diff;
    } else if ('z' - input[i] >= k) {
      c = input[i] + k;
      output[i] = c;
      k = 0;
    } else if (input[i] - 'a' >= k) {
      c = input[i] - k;
      output[i] = c;
      k = 0;
    } else {
      f = false;
      break;
    }
  }
  output[n] = '\0';
  if (f && k == 0)
    printf("%s\n", output);
  else
    printf("-1\n");
  return 0;
}
