#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <limits>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define eprintf(...) 42
#endif
using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vvvll = std::vector<vvll>;
#define reps(i, S, E) for (ll i = (S); i <= (E); i++)
#define rep(i, N) reps(i, 0, N-1)
#define deps(i, E, S) for (ll i = (E); i >= (S); i--)
#define dep(i, N) deps(i, N-1, 0)
const ll INF = 1LL << 60;
const int INF_INT = 1 << 30;

template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
struct mll {
	static ll MOD;
	ll val;
	mll(ll v = 0) : val(v % MOD) { if (val < 0) val += MOD; }
	mll operator - () const { return -val; }
	mll operator + (const mll &b) const { return val + b.val; }
	mll operator - (const mll &b) const { return val - b.val; }
	mll operator * (const mll &b) const { return val * b.val; }
	mll operator / (const mll &b) const { return mll(*this) /= b; }
	mll operator + (ll b) const { return *this + mll(b); }
	mll operator - (ll b) const { return *this - mll(b); }
	mll operator * (ll b) const { return *this * mll(b); }
	friend mll operator + (ll a, const mll &b) { return b + a; }
	friend mll operator - (ll a, const mll &b) { return -b + a; }
	friend mll operator * (ll a, const mll &b) { return b * a; }
	mll &operator += (const mll &b) { val = (val + b.val) % MOD; return *this; }
	mll &operator -= (const mll &b) { val = (val + MOD - b.val) % MOD; return *this; }
	mll &operator *= (const mll &b) { val = (val*b.val) % MOD; return *this; }
	mll &operator /= (const mll &b) {
		ll c = b.val, d = MOD, u = 1, v = 0;
		while (d) {
			ll t = c / d;
			c -= t * d; swap(c, d);
			u -= t * v; swap(u, v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll &operator += (ll b) { return *this += mll(b); }
	mll &operator -= (ll b) { return *this -= mll(b); }
	mll &operator *= (ll b) { return *this *= mll(b); }
	mll &operator /= (ll b) { return *this /= mll(b); }
	bool operator == (const mll &b) { return val == b.val; }
	bool operator != (const mll &b) { return val != b.val; }
	bool operator == (ll b) { return *this == mll(b); }
	bool operator != (ll b) { return *this != mll(b); }
	friend bool operator == (ll a, const mll &b) { return mll(a) == b.val; }
	friend bool operator != (ll a, const mll &b) { return mll(a) != b.val; }
	friend ostream &operator << (ostream &os, const mll &a) { return os << a.val; }
	friend istream &operator >> (istream &is, mll &a) { return is >> a.val; }
	static mll Combination(ll a, ll b) {
		chmin(b, a - b);
		if (b < 0) return mll(0);
		mll c = 1;
		rep(i, b) c *= a - i;
		rep(i, b) c /= i + 1;
		return c;
	}
};
using vmll = std::vector<mll>;
using vvmll = std::vector<vmll>;
using vvvmll = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;

struct Fast {
	Fast() {
		cin.tie(0);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(std::numeric_limits<double>::max_digits10);
	}
} fast; //cin,cout�������̂��܂��Ȃ��{�����w��

ll mll::MOD = (ll)(1e9 + 7);// 998244353ll;


//B
ll N;
ll M;
ll V;
ll P;
vll A(0);

// index �������𖞂������ǂ���
bool isOK(ll score) { //score���p�X���邩����
	ll X = upper_bound(A.begin(), A.end(), score) - A.begin() - 1ll; //UB��index���傫���ŏ���index��Ԃ��̂�-1

	//���łɏ��P�ȓ��̏ꍇ��ok
	if (N - X <= P) {
		return true;
	}

	ll Y = upper_bound(A.begin(), A.end(), score + M) - A.begin();

	//M�l�����[���Ă�����Ȃ��ꍇ��ng
	if (N - Y >= P) {
		return false;
	}

	ll kakuteiVote = (X + 1) * M + (P - 1) * M;
	ll floatVote = M * V - kakuteiVote;
	ll upperlimitVote = 0;

	reps(i, X + 1, N - (P - 1) - 1) {
		upperlimitVote += (score + M - A[i]);
	}

	eprintf("score:%lld X:%lld Y:%lld kakuteiVote:%lld floatVote:%lld upperlimitVote:%lld %s\n",
				score, X, Y, kakuteiVote, floatVote, upperlimitVote, floatVote <= upperlimitVote ? "ok" : "ng");

	if (floatVote <= upperlimitVote) {
		return true;
	}
	else {
		return false;
	}
}

// �ėp�I�ȓ񕪒T���̃e���v��
ll binary_search() { //�I�΂��\���̂���ŏ��̏����X�R�A�����߂�
	ll ng = -1; // 0�������𖞂������Ƃ�����̂ŁA�����l�� -1
	ll ok = 1000000001; // �ő�X�R�A+1

	// ok �� ng �̂ǂ��炪�傫�����킩��Ȃ����Ƃ��l��
	while (abs(ok - ng) > 1) {
		ll mid = (ok + ng) / 2;
		if (isOK(mid)) {
			ok = mid;
		}
		else {
			ng = mid;
		}
	}
	return ok;
}

int main() {
	cin >> N; 
	cin >> M;
	cin >> V;
	cin >> P;
	A.resize(N);
	rep(i, N) {
		cin >> A[i];
	}

	std::sort(A.begin(), A.end());

	eprintf("A: ");
	rep(i, N) {
		eprintf("%lld ", A[i]);
	}
	eprintf("\n");

	ll okScore = binary_search();

	ll result = N - (lower_bound(A.begin(), A.end(), okScore) - A.begin());

	cout << result << endl;

	return 0;
}


//A
/*
int main() {
	ll N;
	cin >> N;
	ll A;
	cin >> A;
	ll B;
	cin >> B;

	ll result = 0;

	if (abs(A - B) % 2 == 0) {
		result = abs(A - B) / 2;
	}
	else {
		//ll dis1 = max(A - 1, B - 1);
		//ll dis2 = max(N - A, N - B);
		//ll ans1 = min(dis1, dis2);
		ll ans1 = 0;

		if (A < B) {
			ll temp = A - 1 + 1; //�����킹1��
			ll Bpos = B - temp;
			ans1 = (Bpos - 1) / 2 + temp;
		}
		else {
			ll temp = B - 1 + 1; //�����킹1��
			ll Apos = A - temp;
			ans1 = (Apos - 1) / 2 + temp;
		}

		ll ans2 = 0;
		if (A < B) {
			ll temp = N - B + 1; //�����킹1��
			ll Apos = A + temp;
			ans2 = (N - Apos) / 2 + temp;
		}
		else {
			ll temp = N - A + 1; //�����킹1��
			ll Bpos = B + temp;
			ans2 = (N - Bpos) / 2 + temp;
		}

		result = min(ans1, ans2);
	}

	cout << result << endl;

	return 0;
}
*/

Measured memory_bytes: 1024