#include <iostream>
#include <algorithm>
#include <vector>
#define int long long
using namespace std;

int arr[100010],qwq[100010];

signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	int n,m,v,p,i;
	cin>>n>>m>>v>>p;
	for(i=0;i<n;i++)
	{
		cin>>arr[i];
	}
	sort(arr,arr+n);
	for(i=n-p-1;i>=0;i--)
	{
		qwq[i]=qwq[i+1]+arr[i+1];
	}
	int ans=0;
	for(i=0;i<n;i++)
	{
		if(i>=n-p)
			ans++;
		else if((arr[i]+m)*(n-p-i)>=(qwq[i]+max((int)0,n-p-i-(n-v))*m) && arr[i]+m>=arr[n-p])
			ans++;
	}
	cout<<ans<<'\n';
	
	return 0;
}