#include <bits/stdc++.h>
#define endl "\n"
using namespace std;
#define ll long long
#define ld long double
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define repo(i,n) for(int i = 1; i < (int)(n); i++)
#define pb push_back
#define mp make_pair
#define np next_permutation
#define fi first
#define se second
#define all(x) (x).begin(),(x).end()
#define uniq(v) v.erase(unique(v.begin(),v.end()),v.end())
#define lb(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define ub(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
using Pair = pair<ll,pair<int,int>>;
#define pq priority_queue<Pair, vector<Pair>, greater<Pair>> 
const ll mod=1000000007;
//const ll mod=998244353;
const ld pi=acos(-1.0);
const ll INF = 1LL<<61;
template<class T>bool chmax(T &a, const T &b) { 
  if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) {
  if (b<a) { a=b; return 1; } return 0; }
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }
//intの最大値2147483647 ≒ 2×10^9
//long longの最大値9223372036854775807 ≒ 9×10^18
//'大文字'+=32;    で小文字に
//  cout << fixed << setprecision (20);   小数点以下2０桁まで
//実行時間制約2秒では２×10^8回くらいまで計算できる



int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  ll n,m,v,p;
  cin>>n>>m>>v>>p;

  vector<ll> q(n);
  rep(i,n){
    cin>>q[i];
  }

  sort(all(q));
  reverse(all(q));

//————————————————二分探索——————————————————————————

  int ng = n;
  int ok = p-1;
  while (abs(ok - ng) > 1) {
    int mid = (ng + ok) / 2;

    ll x=q[mid]+m;

    if(x<q[p-1]){
      ng=mid;
      continue;
    }

    int cnt=n-mid+p-1;
    ll hyo=m*cnt;

    for(int i=p-1;i<mid;i++){
      hyo+=x-q[i];
    }

    (m*v<=hyo? ok : ng) = mid;
  }

  cout << ok+1 << endl;

//——————————————————————————————————————————


}
#include<bits/stdc++.h>
using namespace std;
template<typename T>inline T read(){
	T f=0,x=0;char c=getchar();
	while(!isdigit(c)) f=c=='-',c=getchar();
	while(isdigit(c)) x=x*10+c-48,c=getchar();
	return f?-x:x;
}
#define int long long
namespace run{
	const int N=2e5+9;
	int a[N],m,v,p,n,ans,sum[N];
	int main(){
		n=read<int>(),m=read<int>(),v=read<int>(),ans=p=read<int>();
		for(int i=1;i<=n;i++) a[i]=read<int>();
		sort(a+1,a+n+1);
		for(int i=1;i<=n;i++) sum[i]=sum[i-1]+a[i];
	//	for(int i=1;i<=n;i++) cout<<a[i]<<" ";cout<<endl;
		for(int i=1;i<=n-p;i++){
			if(m+a[i]<a[n-p+1]) continue;
			else{
				int tmp=(p-1+i)*m+((n-p+1-i)*(a[i]+m)-(sum[n-p+1]-sum[i]));
			//	cout<<tmp<<endl;
				if(tmp>=m*v) ans++;
			}
		}
		printf("%lld\n",ans);
		return 0;
	}
}
#undef int
int main(){
#ifdef my
	freopen(".in","r",stdin);
	freopen(".out","w",stdout);
#endif
	return run::main();
}