#include <bits/stdc++.h>
using namespace std;
template <class T>
inline bool read(T &x) {
  int c = getchar();
  int sgn = 1;
  while (~c && c < '0' || c > '9') {
    if (c == '-') sgn = -1;
    c = getchar();
  }
  for (x = 0; ~c && '0' <= c && c <= '9'; c = getchar()) x = x * 10 + c - '0';
  x *= sgn;
  return ~c;
}
int X[] = {-1, -1, -1, 0, 1, 1, 1, 0};
int Y[] = {-1, 0, +1, 1, 1, 0, -1, -1};
int n, k;
string str;
string ans;
int main() {
  cin >> n >> k;
  cin >> str;
  ans = str;
  for (int i = 0; i < n; i++) {
    int need = 0;
    char t = str[i];
    for (char c = 'a'; c <= 'z'; c++) {
      int diff = abs(str[i] - c);
      if (diff <= k and diff > need) {
        need = diff;
        t = c;
      }
    }
    k -= need;
    ans[i] = t;
  }
  if (k)
    cout << "-1" << endl;
  else
    cout << ans << endl;
  return 0;
}
