#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1);
const int N = (int)2e5 + 7, mod = 1000000007, M = 2e9;
int n, k, a, m, node[N], cnt, t;
struct bit {
  void update(int x) {
    while (x <= n) {
      node[x]++;
      x += x & -x;
    }
  }
  int get(int x) {
    int c = 0;
    while (x) {
      c += node[x];
      x -= x & -x;
    }
    return c;
  }
  int bs(int x) {
    int st = 1, en = n + 1, mid;
    while (st < en) {
      mid = (st + en) >> 1;
      if (get(mid) < x)
        st = mid + 1;
      else
        en = mid;
    }
    return st;
  }
  bool insrt(int x) {
    int w = get(x), y = bs(w), z = bs(w + 1) - 1, v = (z - y + 2) / a;
    cnt -= v;
    v = (z - x + 1) / a + (x - y + 1) / a;
    cnt += v;
    update(x);
    update(x + 1);
    return cnt < k;
  }
} x;
int main() {
  scanf("%d%d%d%d", &n, &k, &a, &m);
  a++;
  node[n + 1] = 2 * N;
  cnt = (n + 1) / a;
  for (int i = 1; i <= m; i++) {
    scanf("%d", &t);
    if (x.insrt(t)) {
      cout << i;
      return 0;
    }
  }
  cout << -1;
  return 0;
}
