#include <bits/stdc++.h>
using namespace std;
int n, k;
string s, ans;
int main() {
  cin >> n >> k >> s;
  for (int i = 0; i < n; ++i) {
    int x, y;
    if ('z' - s[i] > s[i] - 'a') {
      x = 'z' - s[i], y = s[i] - 'a';
      if (s[i] + k <= 'z')
        ans += char(s[i] + k), k = 0;
      else if (s[i] - k >= 'a')
        ans += char(s[i] - k), k = 0;
      else if (k >= x)
        ans += 'z', k -= x;
      else if (k >= y)
        ans += 'a', k -= y;
    } else {
      x = s[i] - 'a', y = 'z' - s[i];
      if (s[i] + k <= 'z')
        ans += char(s[i] + k), k = 0;
      else if (s[i] - k >= 'a')
        ans += char(s[i] - k), k = 0;
      else if (k >= x)
        ans += 'a', k -= x;
      else if (k >= y)
        ans += 'z', k -= y;
    }
  }
  if (k)
    cout << -1;
  else
    cout << ans;
}
