#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector")
#pragma GCC target("sse,sse2,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
const int MOD = 1e9 + 7;
const int INF32 = 1 << 30;
const long long INF64 = 1LL << 60;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, k;
  cin >> n >> k;
  string s, ans = "";
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (!k)
      ans += s[i];
    else if (k >= max('z' - s[i], s[i] - 'a')) {
      k -= max('z' - s[i], s[i] - 'a');
      if ('z' - s[i] >= s[i] - 'a')
        ans += 'z';
      else
        ans += 'a';
    } else {
      if (s[i] - k >= 'a')
        ans += (char)(s[i] - k);
      else
        ans += (char)(s[i] + k);
      k = 0;
    }
  }
  cout << (k ? "-1" : ans);
  return 0;
}
