#include <bits/stdc++.h>
using namespace std;
string s;
vector<long long int> myvector;
long long int power(long long int a, long long int b) {
  long long int ans = 1;
  while (b > 0) {
    if (b & 1) {
      ans *= a;
    }
    a *= a;
    b /= 2;
  }
  return ans;
}
long long int answer = 0;
long long int n, k;
string ss;
int main() {
  cin >> n >> k;
  cin >> s;
  for (long long int i = 0; i < n; i++) {
    long long int u, l;
    u = s[i];
    l = s[i];
    while (abs(u - s[i]) <= k && u <= 122) u++;
    while (abs(l - s[i]) <= k && l >= 97) l--;
    u--;
    l++;
    if (abs(u - s[i]) > abs(l - s[i])) {
      ss += u;
      k -= abs(u - s[i]);
    } else {
      ss += l;
      k -= abs(l - s[i]);
    }
  }
  if (k == 0)
    cout << ss;
  else
    cout << "-1";
  return 0;
}
