#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, k;
  cin >> n >> m >> k;
  int count = 0;
  vector<int> list;
  bool flag = false;
  for (int i = 0; i < n; i++) {
    int temp;
    cin >> temp;
    list.push_back(temp);
  }
  sort(list.begin(), list.end());
  int i = n - 1;
  if (m <= k) {
    cout << "0";
    return 0;
  } else
    k = k - 1;
  while (i >= 0) {
    count++;
    int diff = m - list[i];
    i--;
    if (diff > k) {
      m = diff + 1;
    } else {
      cout << count;
      flag = true;
      break;
    }
  }
  if (!flag && m > 0) cout << "-1";
  return 0;
}
