#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ii = pair<int, int>;
const int MAX{200010};
const ll MOD{1000000007}, oo{1LL << 62};
int dist(int N, const string& a, const string& b) {
  int d = 0;
  for (int i = 0; i < N; ++i) d += abs(a[i] - b[i]);
  return d;
}
string solve(int N, int K, const string& s) {
  string ans(s);
  for (int i = 0; K and i < N; ++i) {
    int ord = s[i] - 'a';
    int maxd = max(abs(25 - ord), ord);
    int d = min(maxd, K);
    K -= d;
    ans[i] = (ord + d <= 25 ? 'a' + ord + d : 'a' + ord - d);
  }
  return K ? "-1" : ans;
}
int main() {
  ios::sync_with_stdio(false);
  int N, K;
  string s;
  cin >> N >> K >> s;
  auto ans = solve(N, K, s);
  cout << ans << '\n';
  return 0;
}
