#include <bits/stdc++.h>
using namespace std;
int n, k, a, m;
int stone[200005];
int road[200005];
bool ok(int x) {
  memset(road, 0, sizeof road);
  for (int i = 1; i <= x; i++) road[stone[i]] = 1;
  int cnt = 0;
  int l = 0;
  for (int i = 1; i <= n; i++) {
    if (road[i] == 1) {
      l = 0;
      continue;
    }
    l++;
    if (l == a) {
      cnt++;
      l = -1;
    }
  }
  return cnt >= k;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n >> k >> a;
  cin >> m;
  for (int i = 1; i <= m; i++) cin >> stone[i];
  int lo = 0, hi = m + 1;
  while (hi - lo > 1) {
    int mid = (lo + hi) / 2;
    if (ok(mid))
      lo = mid;
    else
      hi = mid;
  }
  if (hi == m + 1)
    cout << -1 << '\n';
  else
    cout << hi << '\n';
  return 0;
}
