#include <bits/stdc++.h>
using namespace std;
bool cmp(pair<double, long long int> a, pair<double, long long int> b) {
  if (a.first > b.first)
    return true;
  else if (a.first == b.first) {
    if (a.second < b.second) return true;
  }
  return false;
}
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int lcm(long long int a, long long int b) {
  return (a / gcd(a, b)) * b;
}
bool isPowerOfTwo(int n) {
  if (n == 0) return false;
  return (ceil(log2(n)) == floor(log2(n)));
}
int a[100010];
void solve() {
  long long int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  for (long long int i = 0; i < s.length(); i++) {
    if (s[i] + k > 'z') {
      if (s[i] - k < 'a' && s[i] - 'a' > 'z' - s[i]) {
        k -= (s[i] - 'a');
        s[i] = 'a';
      } else if (s[i] + k > 'z' && 'z' - s[i] > s[i] - 'a') {
        k -= ('z' - s[i]);
        s[i] = 'z';
      } else {
        s[i] = s[i] - k;
        k = 0;
        break;
      }
    } else {
      s[i] = s[i] + k;
      k = 0;
      break;
    }
  }
  if (k > 0)
    cout << -1;
  else
    cout << s;
}
int main() {
  solve();
  return 0;
}
