#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, k;
  cin >> n >> m >> k;
  int a[n];
  int sum = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    sum += a[i];
  }
  if ((sum + k) - n < m) {
    cout << -1 << endl;
    return 0;
  }
  if (k == m) {
    cout << 0 << endl;
    return 0;
  }
  sort(a, a + n, greater<int>());
  int idx = 0;
  int p = k;
  int c = 0;
  while (p < m) {
    p += (a[idx++] - 1);
    c++;
  }
  cout << c << endl;
}
