#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<int>;
using VL = vector<ll>;
template<class T> using PQ = priority_queue<T, vector<T>, greater<T>>;
#define FOR(i,a,n) for(int (i)=(a);(i)<(n);++(i))
#define eFOR(i,a,n) for(int (i)=(a);(i)<=(n);++(i))
#define rFOR(i,a,n) for(int (i)=(n)-1;(i)>=(a);--(i))
#define erFOR(i,a,n) for(int (i)=(n);(i)>=(a);--(i))
#define each(i, a) for(auto &i : a)
#define SORT(i) sort((i).begin(),(i).end())
#define rSORT(i,a) sort((i).begin(),(i).end(),(a))
#define all(i) (i).begin(),(i).end()
#define out(y,x) ((y) < 0 || h <= (y) || (x) < 0 || w <= (x))
#define line cout << "------------------------\n" 
#define ENDL(i,n) ((i) == (n) - 1 ? "\n" : " ")
#define stop system("pause")
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
const long double pi = acos(-1);
const long double eps = 1e-10;
template<class T>inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; }return 0; }
template<class T>inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; }return 0; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, vector<T>& v) { for (auto& elemnt : v)is >> elemnt; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline vector<T> vec(size_t a) { return vector<T>(a); }
template<class T>inline vector<T> defvec(T def, size_t a) { return vector<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return vector<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }

class segtree {
    int n = 1; VL dat;
#define def 0
public:
    segtree(int _n) {
        while (n < _n)n *= 2;
        dat.resize(2 * n, def);
    }
    segtree(VL a) {
        int _n = a.size();
        while (n < _n)n *= 2;
        dat.resize(2 * n, def);
        FOR(i, 0, _n)dat[i + n] = a[i];
        rFOR(i, 1, n)dat[i] = fun(dat[2 * i], dat[2 * i + 1]);
    }

    ll fun(ll x, ll y) { return x + y; }

    void update(int i, ll a) {
        i += n;
        dat[i] = a;
        while (i > 1) {
            i /= 2;
            dat[i] = fun(dat[2 * i], dat[2 * i + 1]);
        }
    }

    ll value(int l, int r) {
        l += n, r += n;

        ll ret = def;
        for (; l < r; l /= 2, r /= 2) {
            if (l & 1) {
                ret = fun(ret, dat[l]);
                l++;
            }
            if (r & 1) {
                --r;
                ret = fun(ret, dat[r]);
            }
        }

        return ret;
    }

    ll operator[](int k) { return dat[k + n]; }
};


int main() {
    init();

    ll n, m, v, p; cin >> n >> m >> v >> p;
    VL a(n); cin >> a;

    SORT(a);
    auto solve = [&](ll x) {
        ll y = x + m, cnt = v * m - m;
        bool use = false;
        VL over; ll overcnt = 0;
        FOR(i, 0, n) {
            if (a[i] == x && !use) {
                use = true;
                continue;
            }
            else if (y < a[i]) {
                ++overcnt;
                cnt -= m;
            }
            else if (y - a[i] < m) {
                cnt -= y - a[i];
                over.push_back(m - y + a[i]);
            }
            else cnt -= m;
        }

        rSORT(over, greater<ll>());
        for (int i = 0; i < over.size() && 0 < cnt; ++i) {
            cnt -= over[i];
            ++overcnt;
        }
        return overcnt; 
    };

    ll ok = n, ng = -1;
    while (ok - ng > 1) {
        ll mid = (ok + ng) / 2;
        if (solve(a[mid]) < p)ok = mid;
        else ng = mid;
    }

    int ans = 0;
    FOR(i, 0, n)if (a[ok] <= a[i])++ans;
    cout << ans << "\n";
}


Measured memory_bytes: 2904