#include <bits/stdc++.h>
using namespace std;
const long double pi = 3.141593;
const long long mod = 1e9 + 7;
vector<long long> adj[200000];
int32_t main() {
  long long n, k, sum = 0;
  cin >> n >> k;
  string s, q = "";
  cin >> s;
  vector<pair<long long, char>> a(27);
  for (long long i = 1; i <= 26; i++) {
    a[i].first = max(26 - i, i - 1);
    if ((26 - i) > (i - 1))
      a[i].second = 'z';
    else
      a[i].second = 'a';
  }
  for (long long i = 0; i < n; i++) sum += a[s[i] - 'a' + 1].first;
  if (k > sum)
    cout << -1 << "\n";
  else {
    for (long long i = 0; i < n; i++) {
      if (k >= a[s[i] - 'a' + 1].first) {
        q += a[s[i] - 'a' + 1].second;
        k -= a[s[i] - 'a' + 1].first;
      } else {
        if (k <= (26 - s[i] + 'a' - 1))
          q += (s[i] + k);
        else
          q += (s[i] - k);
        k = 0;
      }
    }
    cout << q << "\n";
  }
}
