#include <bits/stdc++.h>

#define M_PI 3.14159265358979323846

using namespace std;

//typedef
//-------------------------#include <bits/stdc++.h>

#define M_PI 3.14159265358979323846

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s)
{
    int v;
    istringstream sin(s);
    sin >> v;
    return v;
}
template <class T>
inline string toString(T x)
{
    ostringstream sout;
    sout << x;
    return sout.str();
}
inline int readInt()
{
    int x;
    scanf("%d", &x);
    return x;
}

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<int, PII> TIII;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;

//container util

//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SQ(a) ((a) * (a))
#define EACH(i, c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

//repetition
//------------------------------------------
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define MOD 1000000007

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto &a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
const double EPS = 1E-8;

#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
const int INF = 100000000;

struct Edge
{
    int to, from;
    ll cost;
    Edge(int from, int to, ll cost) : from(from), to(to), cost(cost) {}
};

class UnionFind
{
public:
    vector<ll> par;
    vector<ll> siz;

    vector<ll> maxv;
    UnionFind(ll sz_) : par(sz_), siz(sz_, 1LL)
    {
        for (ll i = 0; i < sz_; ++i)
            par[i] = i;
    }
    void init(ll sz_)
    {
        par.resize(sz_);
        siz.assign(sz_, 1LL);
        for (ll i = 0; i < sz_; ++i)
            par[i] = i;
    }

    ll root(ll x)
    {
        while (par[x] != x)
        {
            x = par[x] = par[par[x]];
        }
        return x;
    }

    bool merge(ll x, ll y)
    {
        x = root(x);
        y = root(y);
        if (x == y)
            return false;
        if (siz[x] < siz[y])
            swap(x, y);
        siz[x] += siz[y];
        par[y] = x;
        return true;
    }

    bool issame(ll x, ll y)
    {
        return root(x) == root(y);
    }

    ll size(ll x)
    {
        return siz[root(x)];
    }
};

typedef vector<vector<Edge>> AdjList;
AdjList graph;

ll mod_pow(ll x, ll n, ll mod)
{
    ll res = 1;
    bool c = false;
    while (n)
    {
        if (n & 1)
            res = res * x;

        if (res > mod)
        {
            c = true;
            res %= mod;
        }
        x = x * x % mod;
        n >>= 1;
    }
    if (c)
        return mod;
    return res;
}

#define SIEVE_SIZE 5000000 + 10
bool sieve[SIEVE_SIZE];
void make_sieve()
{
    for (int i = 0; i < SIEVE_SIZE; ++i)
        sieve[i] = true;
    sieve[0] = sieve[1] = false;
    for (int i = 2; i * i < SIEVE_SIZE; ++i)
        if (sieve[i])
            for (int j = 2; i * j < SIEVE_SIZE; ++j)
                sieve[i * j] = false;
}

bool isprime(ll n)
{
    if (n == 0 || n == 1)
        return false;
    for (ll i = 2; i * i <= n; ++i)
        if (n % i == 0)
            return false;
    return true;
}

template <typename T>
vector<T> gauss_jordan(const vector<vector<T>> &A, const vector<T> &b)
{
    int n = A.size();
    vector<vector<T>> B(n, vector<T>(n + 1));

    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < n; ++j)
        {
            B[i][j] = A[i][j];
        }
    }

    for (int i = 0; i < n; ++i)
        B[i][n] = b[i];

    for (int i = 0; i < n; ++i)
    {
        int pivot = i;
        for (int j = i; j < n; ++j)
        {
            if (abs(B[j][i]) > abs(B[pivot][i]))
                pivot = j;
        }
        swap(B[i], B[pivot]);

        if (abs(B[i][i]) < EPS)
            return vector<T>(); //解なし

        for (int j = i + 1; j <= n; ++j)
            B[i][j] /= B[i][i];
        for (int j = 0; j < n; ++j)
        {
            if (i != j)
            {
                for (int k = i + 1; k <= n; ++k)
                    B[j][k] -= B[i][j] * B[i][k];
            }
        }
    }

    vector<T> x(n);

    for (int i = 0; i < n; ++i)
        x[i] = B[i][n];
    return x;
}

typedef vector<ll> vec;
typedef vector<vec> mat;

mat mul(mat &A, mat &B)
{
    mat C(A.size(), vec((int)B[0].size()));
    for (int i = 0; i < A.size(); ++i)
    {
        for (int k = 0; k < B.size(); ++k)
        {
            for (int j = 0; j < B[0].size(); ++j)
            {
                C[i][j] = (C[i][j] + A[i][k] * B[k][j] % MOD) % MOD;
            }
        }
    }
    return C;
}
mat mat_pow(mat A, ll n)
{
    mat B(A.size(), vec((int)A.size()));

    for (int i = 0; i < A.size(); ++i)
    {
        B[i][i] = 1;
    }

    while (n > 0)
    {
        if (n & 1)
            B = mul(B, A);
        A = mul(A, A);
        n >>= 1;
    }
    return B;
}

bool operator<(const pii &a, const pii &b)
{
    if (a.first == b.first)
        return a.second < b.second;
    return a.first < b.first;
}

const int MAX = 510000;
long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit()
{
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++)
    {
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
long long COM(int n, int k)
{
    if (n < k)
        return 0;
    if (n < 0 || k < 0)
        return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

int bit[1000010];
int sums(int i)
{
    i++;
    int s = 0;
    while (i > 0)
    {
        s += bit[i];
        i -= i & -i;
    }
    return s;
}
void add(int i, int x)
{
    i++;
    while (i <= 1000010)
    {
        bit[i] += x;
        i += i & -i;
    }
}
long long extGCD(long long a, long long b, long long &x, long long &y)
{
    if (b == 0)
    {
        x = 1;
        y = 0;
        return a;
    }
    long long d = extGCD(b, a % b, y, x);
    y -= a / b * x;
    return d;
}

ll GCD(ll a, ll b)
{

    if (b == 0)
        return a;
    return GCD(b, a % b);
}

struct BipartiteMatching
{
    vector<vector<int>> graph;
    vector<int> match, alive, used;
    int timestamp;

    BipartiteMatching(int n) : graph(n), alive(n, 1), used(n, 0), match(n, -1), timestamp(0) {}

    void add_edge(int u, int v)
    {
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    bool dfs(int idx)
    {
        used[idx] = timestamp;
        for (auto &to : graph[idx])
        {
            int to_match = match[to];
            if (alive[to] == 0)
                continue;
            if (to_match == -1 || (used[to_match] != timestamp && dfs(to_match)))
            {
                match[idx] = to;
                match[to] = idx;
                return true;
            }
        }
        return false;
    }

    int bipartite_matching()
    {
        int ret = 0;
        for (int i = 0; i < graph.size(); i++)
        {
            if (alive[i] == 0)
                continue;
            if (match[i] == -1)
            {
                ++timestamp;
                ret += dfs(i);
            }
        }
        return ret;
    }

    void output()
    {
        for (int i = 0; i < graph.size(); i++)
        {
            if (i < match[i])
            {
                cout << i << "-" << match[i] << endl;
            }
        }
    }
};

ll N, M, V, P;
ll A[100010];
pair<ll, ll> B[100010];
bool C(ll idx)
{
    for (int i = 0; i < N; i++)
    {
        B[i] = make_pair(A[i], i);
    }

    //cout << N << " " << M << " " << V << " " << P << endl;
    B[idx].first += M;

    ll nokori_V = V - 1;
    sort(B, B + N);

    ll nidx = 0;
    ll val = 0;
    for (int i = 0; i < N; i++)
    {
        if (B[i].second == idx)
        {
            nidx = i;
            val = B[i].first;
            break;
        }
    }

    ll bigger = 0, equal = 0;
    for (int i = 0; i < N; i++)
    {
        if (i == nidx)
            continue;

        if (val < B[i].first)
        {
            bigger++;
        }
        if (val == B[i].first)
        {
            equal++;
        }
    }

    if (bigger >= P)
        return false;
    ll times = M;
    ll nokori_P = P - bigger - 1;

    times += bigger * M;

    if (nokori_P <= equal)
    {
        nokori_P = 0;
        times += nokori_P * M;

        for (int i = 0; i < N; i++)
        {
            if (val == B[i].first)
                break;
            times += min(M, val - B[i].first);
        }
    }
    else
    {
        nokori_P -= equal;
        times += equal * M;

        for (int i = N - 1; i >= 0; i--)
        {
            if (val <= B[i].first)
                continue;

            if (min(M, val - B[i].first) == M)
            {
                times += M;
            }
            else
            {
                if (nokori_P)
                {
                    times += M;
                    nokori_P--;
                }
                else
                {
                    times += val - B[i].first;
                }
            }
        }
    }

    //cout << idx << " " << times << " " << M << endl;

    if (times / V >= M)
    {
        return true;
    }
    else
    {
        return false;
    }
}
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);

    cin >> N >> M >> V >> P;
    for (int i = 0; i < N; i++)
    {
        cin >> A[i];
    }
    sort(A, A + N);
    ll lb = -1, ub = N - 1;

    while (ub - lb > 1)
    {
        ll mid = (ub + lb) / 2;

        if (C(mid))
        {
            ub = mid;
        }
        else
        {
            lb = mid;
        }
    }
    cout << N - lb - 1 << endl;
    return 0;
}


Measured memory_bytes: 4480