#include <bits/stdc++.h>
using namespace std;
char s[100003];
int f[100003] = {0};
int g[100003] = {0};
int t = 0;
int kk = 0;
bool mark = 0;
int n = 0;
int k = 0;
void dfs(int x, int sum);
int main() {
  while (cin >> n >> k) {
    cin >> s;
    long long sum = 0;
    mark = 0;
    t = 0;
    for (int i = 0; i < n; i++) {
      sum += (f[i] = max('z' - s[i], s[i] - 'a'));
    }
    if (sum < k) {
      cout << -1 << endl;
      continue;
    }
    dfs(0, 0);
    if (mark) {
      for (int i = 0; i < n; i++) {
        if (s[i] + g[i] <= 'z') {
          printf("%c", s[i] + g[i]);
        } else if (s[i] - g[i] >= 'a') {
          printf("%c", s[i] - g[i]);
        }
      }
      cout << endl;
    } else {
      cout << -1 << endl;
    }
  }
  return 0;
}
void dfs(int x, int sum) {
  if (x > n) return;
  if (mark) return;
  if (x == n && sum == k) {
    mark = 1;
    return;
  }
  if (sum > k) {
    return;
  }
  for (int i = f[x]; i >= 0; i--) {
    if (mark) return;
    g[t++] = i;
    dfs(x + 1, sum + i);
    if (mark) return;
    t--;
  }
}
