#include <bits/stdc++.h>
using namespace std;
const int N = 5 * 1000 * 100 + 5;
int a[N];
int n, k;
int main() {
  scanf("%d %d\n", &n, &k);
  int i, maxx = 0;
  char ch;
  for (i = 1; i <= n; i++) {
    scanf("%c", &ch);
    a[i] = int(ch) - int('a') + 1;
    maxx += max(26 - a[i], a[i] - 1);
  }
  if (maxx < k) {
    printf("-1");
    return 0;
  }
  int need = k, j, currMax, value, pos;
  for (i = 1; i <= n; i++) {
    currMax = 0;
    pos = a[i];
    for (j = 1; j <= 26; j++) {
      if (abs(a[i] - j) > need) {
        continue;
      }
      value = abs(a[i] - j);
      if (value > currMax) {
        pos = j;
        currMax = value;
      }
    }
    need -= currMax;
    printf("%c", char(int('a') + pos - 1));
  }
  return 0;
}
