#include <bits/stdc++.h>
using namespace std;
char str[100010];
int dir[100010], mx[100010];
int main() {
  int N, k, i;
  scanf("%d %d\n", &N, &k);
  int sum = 0;
  for (i = 0; i < N; i++) {
    scanf("%c", str + i);
    mx[i] = max((int)(str[i] - 'a'), (int)('z' - str[i]));
    sum += mx[i];
    if ((str[i] - 'a') > ('z' - str[i]))
      dir[i] = -1;
    else
      dir[i] = 1;
  }
  if (sum < k)
    puts("-1");
  else {
    for (i = 0; i < N; i++) {
      printf("%c", str[i] + min(k, mx[i]) * dir[i]);
      k -= min(k, mx[i]);
    }
    puts("");
  }
  return 0;
}
