#include <bits/stdc++.h>
using namespace std;
const int M = 1e6, N = 2 * (1e5 + 20), MOD = 1e9 + 7, OO = 1e16;
long long m, n, k, x, y, vis[N], bla, cnt, ans, a[N], mx, b[N];
pair<int, int> p[N];
vector<int> v;
set<long long> ss;
string s, t;
vector<vector<int> > G;
int main() {
  cin >> n >> k >> s;
  t = s;
  int i = 0;
  int ok = 0;
  for (i = 0; i < n && k > 0; i++) {
    if ('z' - t[i] >= t[i] - 'a') {
      if ('z' - t[i] > k) {
        ok = 1;
        break;
      }
      t[i] = 'z';
      k -= ('z' - s[i]);
    } else {
      if (t[i] - 'a' > k) {
        ok = 2;
        break;
      }
      t[i] = 'a';
      k -= (s[i] - 'a');
    }
  }
  if (i == n && k > 0) return cout << "-1", 0;
  if (k > 0) {
    if (ok == 1)
      t[i] = s[i] + k;
    else
      t[i] = s[i] - k;
  }
  cout << t;
}
