#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
#define int ll
//#define int __int128
//#define ll __int128
typedef pair<int, int   > pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector< vi > vvi;
typedef vector< vvi > vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;
//typedef complex<double> base;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < (int)(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef RUS_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";

template <class T0, class T1>
inline ostream & operator << (ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1, class T2>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " <<  get<3>(a) << "}";
}

template<class T>
inline ostream & operator << (ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())
        out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}



void smain();

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

#ifdef RUS_HOME
    freopen("input", "r", stdin);
    clock_t start = clock();
#endif
    cout << setprecision(12) << fixed;
    smain();
#ifdef RUS_HOME
    cout << "\n\n\n\nTOTAL EXECUTION TIME: " << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
#endif
    return 0;
}

int n, m, v, p;
bool check(vi a, int pos) {
    vpi kek(n);
    for (int i = 0; i < n; i++) {
        kek[i] = {a[i], i};
    }
    int cnt = (v - 1) * m;
    vector <int> us(n);
    kek[pos].first += m;
    us[pos] = m;
    int ans = 0;
    for (int i = 0; i < n; i++) {
        if (kek[i].first <= kek[pos].first)
            continue;
        int y = min(m, cnt);
        us[i] = y;
        ans++;
        cnt -= y;
    }
    if (ans >= p)
        return false;
    if (cnt == 0)
        return true;
    for (int i = 0; i < n; i++) {
        if (kek[i].first > kek[pos].first || pos == i)
            continue;
        int y = min(min(kek[pos].first - kek[i].first, m), cnt);
        us[i] = y;
        cnt -= y;
    }

    if (cnt == 0)
        return true;

    vi lol;
    for (int i = 0; i < n; i++) {
        if (i == pos || cnt == 0) {
            continue;
        }
        if (us[i] != m) {
            lol.push_back(us[i]);
        }
    }
    sort(ALL(lol));
    for (int i = 0; i < lol.size(); i++) {
        if (cnt == 0)
            break;
        int y = min(m - lol[i], cnt);
        cnt -= y;
        ans++;
    }
    if (ans >= p)
        return false;

    return true;
}

void smain() {


    cin >> n >> m >> v >> p;
    vi a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    sort(RALL(a));

    int l = -1, r = n;
    while (l + 1 < r) {
        int mid = l + r >> 1;
        if (check(a, mid))
            l = mid;
        else
            r = mid;
    }

    cout << l + 1;
}

Measured memory_bytes: 7260