#include <bits/stdc++.h>
using namespace std;
int n, k, a, m, ans = -1, b[200005];
bool used[200005];
int main() {
  scanf("%d%d%d%d", &n, &k, &a, &m);
  for (int i = 0; i < m; i++) scanf("%d", b + i);
  int l = 0, r = m - 1;
  while (l <= r) {
    int mid = (l + r) >> 1, counter = 0, last = 0;
    for (int i = 0; i <= mid; i++) used[b[i] - 1] = true;
    used[n] = true;
    for (int i = 0; i <= n; i++)
      if (used[i])
        counter += (i - last + 1) / (a + 1), used[i] = false, last = i + 1;
    if (k <= counter)
      l = mid + 1;
    else
      r = mid - 1, ans = mid + 1;
  }
  cout << ans;
  return 0;
}
