#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const long long INF = 2e18;
void print(int a[], int n) {
  for (int i = 0; i < n; i++) cout << a[i] << " ";
  cout << "\n";
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int tc = 1;
jump:
  while (tc--) {
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    string t = "";
    for (int i = 0; i < (n); i++) {
      if (k == 0) {
        for (int j = i; j < n; j++) t += s[j];
        break;
      }
      int f = 'z' - s[i];
      int b = s[i] - 'a';
      if (f > b) {
        int x = s[i] + min(f, k);
        t += (char)x;
        k -= min(f, k);
      } else {
        int x = s[i] - min(b, k);
        t += (char)x;
        k -= min(b, k);
      }
    }
    if (k > 0)
      cout << -1;
    else
      cout << t;
  }
}
