#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

typedef long long ll;
ll n, m, v, la, st, cnt, e, w, po, w2, a[100005], s[100005];
int main()
{
	ll i, j;
	cin >> n >> m >> v >> la;
	for (i = 1; i <= n; i++) {
		scanf ("%lld", &a[i]);
	}
	sort(a + 1, a + n + 1);
	st = n - la + 1;
	for (i = st; i >= 1; i--) {
		s[i]= s[i + 1] + a[i];
	}
	for (i = 1; i <= n; i++) {
		if (i >= st) cnt++;
		else {
			e = a[i] + m;
			if (e >= a[st]) {
				w = e * (st - i) - (s[i + 1]);
				po = (la - 1) + i;
				w2 = max(m * (v - po), 0ll);
				if (w >= w2) cnt++;
			}
		}
	}
	cout << cnt << endl;
    return 0;
}
