#include <bits/stdc++.h>
using namespace std;
int n, k, num;
int a[200010];
int vis[200010];
int judge(int mid) {
  for (int i = 1; i <= n; i++) vis[i] = 0;
  for (int i = 1; i <= mid; i++) {
    vis[a[i]] = 1;
  }
  int sum = 0;
  int ok = 0;
  for (int i = 1; i <= n; i++) {
    if (vis[i] == 1) {
      ok = 0;
    } else {
      ok++;
      if (ok >= num) {
        ok -= num;
        sum++;
        i++;
      }
    }
  }
  return sum >= k;
}
int main() {
  scanf("%d%d%d", &n, &k, &num);
  int m;
  scanf("%d", &m);
  for (int i = 1; i <= m; i++) scanf("%d", &a[i]);
  int l = 1, r = m;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (judge(mid)) {
      l = mid + 1;
    } else {
      r = mid - 1;
    }
  }
  if (l == m + 1)
    printf("-1\n");
  else
    printf("%d\n", l);
  return 0;
}
