#include <bits/stdc++.h>
using namespace std;
#define REP(i,b,e) for(int i=(b);i<(e);++i)
#define RREP(i,b,e) for(int i=(b)-1;i>=e;--i)
#define rep(i,e) for(int i=0;i<(e);++i)

constexpr int MOD = 1000000007;
constexpr int INF = 1LL << 30;
constexpr long long LLINF = 1LL << 62;
constexpr double EPS = 1e-9;

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15) << boolalpha;
  }
} initializer;

template<typename T>
istream &operator>>(istream &is, vector<T> &vec) {
  for (T &x : vec) is >> x;
  return is;
}

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "[";
  for (auto it = vec.begin(); it != vec.end(); ++it) {
    if (it != vec.begin()) os << ", ";
    os << *it;
  }
  return os << "]";
}

template<typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &pa) {
  return os << "(" << pa.first << ", " << pa.second << ")";
}

template<typename Tuple, size_t N>
struct TuplePrinter {
  static void print(const Tuple &t) {
    TuplePrinter<Tuple, N-1>::print(t);
    cout << ", " << get<N-1>(t);
  }
};

template<typename Tuple>
struct TuplePrinter<Tuple, 1> {
  static void print(const Tuple &t) {
    cout << get<0>(t);
  }
};

template<typename... T>
ostream &operator<<(ostream &os, const tuple<T...> &tup) {
  os << "(";
  TuplePrinter<decltype(tup), sizeof...(T)>::print(tup);
  return os << ")";
}

template<typename T>
ostream &operator<<(ostream &os, const set<T> &se) {
  os << "{";
  for (auto it = se.begin(); it != se.end(); ++it) {
    if (it != se.begin()) os << ", ";
    os << *it;
  }
  return os << "}";
}

template<typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &ma) {
  os << "{";
  for (auto it = ma.begin(); it != ma.end(); ++it) {
    if (it != ma.begin()) os << ", ";
    os << it->first << ": " << it->second;
  }
  return os << "}";
}

inline void print(void) { cout<<'\n'; }
template<class T> inline void print(const T &x) { cout<<x<<'\n'; }
template<class T, class... U> inline void print(const T &x, const U&... y) { cout<<x<<" "; print(y...); }
#define dump(...) cout<<#__VA_ARGS__<<": [L_"<<__LINE__<<"]"<<'\n'; print(__VA_ARGS__);cout<<'\n';

template<class T, class U>inline bool chmax(T &a, const U &b) { if(a<b){ a=b; return 1; } return 0; }
template<class T, class U>inline bool chmin(T &a, const U &b) { if(b<a){ a=b; return 1; } return 0; }


int main() {
  int n; cin>>n;
  long long m; cin>>m;
  long long v, p; cin>>v>>p;
  vector<long long> a(n);
  rep(i, n) cin>>a[i];
  sort(a.begin(), a.end());

  int ok = -1, ng = n;
  while (ok + 1 < ng) {
    int mid = (ng + ok) / 2;
    bool good = true;
    int t = a[mid] + m;
    int big_idx = lower_bound(a.begin(), a.end(), t+1) - a.begin();
    int big = n - big_idx;
    if (big >= p) good = false;
    int huyaseru = p - (n - (lower_bound(a.begin(), a.end(), t) - a.begin()) + 1);
    long long rem = m * (v - 1 - big);
    int small_idx = lower_bound(a.begin(), a.end(), t) - a.begin();
    int same = big_idx - small_idx;
    rep(i, same) {
      if (big + i + 1 >= p) break;
      if (huyaseru > 0) {
        rem -= m;
        --huyaseru;
      }
    }
    RREP(i, small_idx, 0) {
      if (i == mid) continue;
      if (huyaseru > 0) {
        rem -= m;
        --huyaseru;
      } else {
        rem -= min(m, t - a[i]);
      }
    }
    if (rem > 0) good = false;

    if (good) ng = mid;
    else ok = mid;
  }
  print(n - ng);

  return 0;
}

Measured memory_bytes: 1024