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