#ifdef _MSC_VER
#define _CRT_SECURE_NO_WARNINGS
#  include <intrin.h>
#  define __builtin_popcount __popcnt
#endif

#define _USE_MATH_DEFINES

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <unordered_map>
#include <stack>
#include <list>
#include <math.h>
#include <bitset>
#include <iterator>
#include <map>
#include <iomanip>
#include <functional>
#include <string>
#include <algorithm>
#include <queue>
#include <random>
#include <numeric>
#include <set>
#include <cassert>
#include <cmath>
#include <cinttypes>

using namespace std;

template<class T> ostream& operator<<(ostream& os, const vector<T>& v) { for (auto i = begin(v); i != end(v); i++) os << *i << (i == end(v) - 1 ? "" : " "); return os; }
template<class T> istream& operator>>(istream& is, vector<T>& v) { for (auto i = begin(v); i != end(v); i++) is >> *i; return is;}
struct fast_io {
	fast_io& operator>> (int& target) { scanf("%" PRId32, &target);  return *this; }
	fast_io& operator>> (unsigned int& target) { scanf("%" PRIu32, &target);  return *this; }
	fast_io& operator>> (long long& target) { scanf("%" PRId64, &target);  return *this; }
	fast_io& operator>> (unsigned long long& target) { scanf("%" PRIu64, &target);  return *this; }
	template<typename T> fast_io& operator>> (vector<T>& target) { for (auto& value : target) { *this >> value; } return *this; }
	fast_io& operator<< (const int value) { printf("%" PRId32, value); return *this; }
	fast_io& operator<< (const unsigned int value) { printf("%" PRIu32, value); return *this; }
	fast_io& operator<< (const long long value) { printf("%" PRId64, value); return *this; }
	fast_io& operator<< (const unsigned long long value) { printf("%" PRIu64, value); return *this; }
	fast_io& operator<< (const string& value) { printf("%s", value.c_str()); return *this; }
	template<typename T> fast_io& operator<< (const vector<T>& target) { for (auto& value : target) { *this << value << " "; } return *this; }
}; fast_io fio;

#define MOD 1000000007
#define pii pair<int,int>
#define pll pair<long long, long long>
#define all(x) (x).begin(), (x).end()
#define sort_all(x) sort(all(x))
#define make_unique(x) (x).erase(unique(all(x)), (x).end())


int main() {

#if defined(_DEBUG)
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif

	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	int n;
	long long m, v;
	int p;

	fio >> n >> m >> v >> p;
	vector<int> arr(n);
	fio >> arr;

	sort(all(arr));
	vector<long long> prefs(n);
	prefs[0] = arr[0];
	for (int i = 1; i < n; i++) prefs[i] = prefs[i - 1] + arr[i];

	int ans = 0;
	for (int i = 0; i < n; i++)
	{
		auto it = upper_bound(all(arr), arr[i] + m);
		int right_b = n;
		if (it != arr.end()) right_b = it - arr.begin();

		right_b = min(right_b, n - (p - 1));
		right_b = max(right_b, i + 1);
		long long bigger = n - right_b;
		if (bigger >= p)
			continue;

		long long total = v * m - m;
		long long potential = (long long)(n - right_b) * m;
		potential += (long long)i * m;

		long long len = right_b - i - 1;
		if (len > 0)
		{
			potential += m * len - (prefs[right_b - 1] - prefs[i] - (long long)arr[i]*len);
		}

		if (total <= potential)
			ans++;
	}

	fio << ans;
	//printf("%d", ans);

	return 0;
}

Measured memory_bytes: 1408