#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.sync_with_stdio(0);
  long long n, diff;
  cin >> n >> diff;
  string s;
  cin >> s;
  string res;
  for (long long i = 0; i < (n); i++) {
    char pis = s[i];
    long long smer = 1;
    if (abs((long long)(pis - 'a')) > abs((long long)(pis - 'z'))) {
      res += 'a';
      smer = 1;
    } else {
      res += 'z';
      smer = -1;
    }
    long long r = abs((long long)(pis - res[((long long)(res).size()) - 1]));
    while (r > diff) {
      res[((long long)(res).size()) - 1] += smer;
      r--;
    }
    diff -= r;
  }
  if (diff > 0)
    cout << -1 << endl;
  else
    cout << res << endl;
  return 0;
}
