#include <bits/stdc++.h>
using namespace std;
const int inf = (int)1.01e9;
const double eps = 1e-9;
const int maxn = (int)2e5 + 10;
set<int> S;
int main() {
  int n, k, a;
  scanf("%d%d%d", &n, &k, &a);
  int cur = (n + 1) / (a + 1);
  assert(cur >= k);
  int m;
  scanf("%d", &m);
  for (int i = 0; (i) < (m); ++i) {
    int x;
    scanf("%d", &x);
    set<int>::iterator it = S.lower_bound(x);
    int left = 0;
    int right = n + 1;
    if (it != S.end()) {
      right = *it;
    }
    if (it != S.begin()) {
      --it;
      left = *it;
    }
    cur -= (right - left) / (a + 1);
    cur += (x - left) / (a + 1);
    cur += (right - x) / (a + 1);
    if (cur < k) {
      printf("%d\n", i + 1);
      return 0;
    }
    S.insert(x);
  }
  printf("-1\n");
  return 0;
}
