#include <bits/stdc++.h>
using namespace std;
int main() {
  int filterCount, devCount, socketCount;
  cin >> filterCount >> devCount >> socketCount;
  int *filters = new int[filterCount];
  for (int i = 0; i < filterCount; i++) cin >> filters[i];
  sort(filters, filters + filterCount, greater<int>());
  if (devCount <= socketCount) {
    cout << 0;
    return 0;
  }
  for (int i = 0; i < filterCount; i++) {
    socketCount += filters[i];
    socketCount--;
    if (socketCount < 0) {
      cout << -1;
      return 0;
    }
    if (devCount <= socketCount) {
      cout << i + 1;
      return 0;
    }
  }
  cout << -1;
  return 0;
}
