#include <bits/stdc++.h>
using namespace std;
int n;
char a[1000000];
char b[1000000];
int k;
char shift(char x) { return max('z' - x, x - 'a'); }
int main() {
  int i, j, fl, test;
  scanf("%d%d", &n, &k);
  scanf("%s", a);
  for (i = 0; i < n; i++) {
    if (shift(a[i]) <= k) {
      if ('z' - a[i] > a[i] - 'a')
        b[i] = 'z';
      else
        b[i] = 'a';
      k -= shift(a[i]);
    } else {
      if (k + (a[i] - 'a') < 26)
        b[i] = k + a[i];
      else
        b[i] = a[i] - k;
      k = 0;
      break;
    }
  }
  if (k != 0) {
    printf("-1\n");
    return 0;
  }
  while (i < n) {
    i++;
    b[i] = a[i];
  }
  b[n] = '\0';
  printf("%s\n", b);
  return 0;
}
