#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
char s[maxn], t[maxn];
int main() {
  int n, k;
  while (cin >> n >> k) {
    cin >> s;
    for (int i = 0; i < n; ++i) {
      if (s[i] <= 'm') {
        int tmp = min('z' - s[i], k);
        t[i] = s[i] + tmp;
        k -= tmp;
      } else {
        int tmp = min(s[i] - 'a', k);
        t[i] = s[i] - tmp;
        k -= tmp;
      }
    }
    t[n] = 0;
    if (!k)
      cout << t << endl;
    else
      cout << -1 << endl;
  }
  return 0;
}
