#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e5 + 5;
char s[MAX], out[MAX];
int n, k;
int main() {
  scanf("%d%d%s", &n, &k, s);
  for (int i = 0; i < n; ++i) {
    int f = s[i] + k, b = s[i] - k;
    if (f >= 'a' && f <= 'z')
      out[i] = char(f), k = 0;
    else if (b >= 'a' && b <= 'z')
      out[i] = char(b), k = 0;
    else {
      f = 'z' - s[i], b = s[i] - 'a';
      if (f > b)
        out[i] = 'z', k -= f;
      else
        out[i] = 'a', k -= b;
    }
  }
  if (k)
    puts("-1");
  else
    printf("%s\n", out);
}
