#include <bits/stdc++.h>
using namespace std;
int n, m, k, sum;
struct zz {
  int val, id;
} a[200005];
bool cmp(zz x, zz y) { return x.val < y.val; }
bool Check(int x) {
  int tot = 0, l = 0;
  for (int i = 1; i <= m; i++) {
    if (a[i].id <= x) {
      tot += (a[i].val - l) / (sum + 1);
      l = a[i].val;
    }
  }
  tot += (n - l + 1) / (sum + 1);
  return k <= tot;
}
int main() {
  cin >> n >> k >> sum;
  cin >> m;
  for (int i = 1; i <= m; i++) {
    scanf("%d", &a[i].val);
    a[i].id = i;
  }
  sort(a + 1, a + m + 1, cmp);
  int l = 1, r = m;
  int ans = -1;
  while (l <= r) {
    int mid = (l + r) >> 1;
    if (!Check(mid))
      r = mid - 1, ans = mid;
    else
      l = mid + 1;
  }
  cout << ans << endl;
  return 0;
}
