#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, wA, wZ, m, i;
  string s, sNew;
  char c;
  cin >> n >> k >> s;
  sNew = "";
  for (i = 0; i < n && k > 0; i++) {
    c = s[i];
    wA = (int)(c - 'a');
    wZ = (int)('z' - c);
    if (k >= wA && k >= wZ) {
      if (wA > wZ)
        m = -wA;
      else
        m = wZ;
    } else if (k > wZ && k < wA)
      m = -k;
    else
      m = k;
    sNew += (char)(c + m);
    k -= abs(m);
  }
  if (i == n && k > 0)
    cout << -1;
  else {
    for (; i < n; i++) sNew += s[i];
    cout << sNew;
  }
  return 0;
}
