#include <bits/stdc++.h>
using namespace std;
long long i, j, n, k, k1, k2, k3, m, h, z, l, x, y, r;
long long pre[200500], b[1001005];
long long a[300005];
char s[300500];
int main() {
  cin >> n >> k;
  scanf("%s", s);
  long long tmp = 0;
  for (i = 0; i < n; i++) {
    tmp += max('z' - s[i], s[i] - 'a');
    b[i] = max('z' - s[i], s[i] - 'a');
    if ('z' - s[i] > s[i] - 'a')
      a[i] = 1;
    else
      a[i] = -1;
  }
  if (tmp < k) {
    cout << -1 << endl;
    return 0;
  }
  for (i = 0; i < n; i++) {
    s[i] += a[i] * min(k, b[i]);
    k -= min(k, b[i]);
  }
  printf("%s", s);
  return 0;
}
