//#define NDEBUG
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <utility>
#include <vector>

namespace n91 {

using i8 = std::int_fast8_t;
using i32 = std::int_fast32_t;
using i64 = std::int_fast64_t;
using u8 = std::uint_fast8_t;
using u32 = std::uint_fast32_t;
using u64 = std::uint_fast64_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

struct rep {
  struct itr {
    usize i;
    constexpr itr(const usize i) noexcept : i(i) {}
    void operator++() noexcept { ++i; }
    constexpr usize operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
  };
  const itr f, l;
  constexpr rep(const usize f, const usize l) noexcept
      : f(std::min(f, l)), l(l) {}
  constexpr auto begin() const noexcept { return f; }
  constexpr auto end() const noexcept { return l; }
};
struct revrep {
  struct itr {
    usize i;
    constexpr itr(const usize i) noexcept : i(i) {}
    void operator++() noexcept { --i; }
    constexpr usize operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
  };
  const itr f, l;
  constexpr revrep(const usize f, const usize l) noexcept
      : f(l - 1), l(std::min(f, l) - 1) {}
  constexpr auto begin() const noexcept { return f; }
  constexpr auto end() const noexcept { return l; }
};
template <class T> auto md_vec(const usize n, const T &value) {
  return std::vector<T>(n, value);
}
template <class... Args> auto md_vec(const usize n, Args... args) {
  return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
}
template <class T> constexpr T difference(const T &a, const T &b) noexcept {
  if (a < b) {
    return b - a;
  } else {
    return a - b;
  }
}
template <class T> void chmin(T &a, const T &b) noexcept {
  if (b < a) {
    a = b;
  }
}
template <class T> void chmax(T &a, const T &b) noexcept {
  if (a < b) {
    a = b;
  }
}
template <class F> class fix_point : private F {
public:
  explicit constexpr fix_point(F &&f) : F(std::forward<F>(f)) {}

  template <class... Args>
  constexpr decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, std::forward<Args>(args)...);
  }
};
template <class F> constexpr decltype(auto) make_fix(F &&f) {
  return fix_point<F>(std::forward<F>(f));
}
template <class T> T scan() {
  T ret;
  std::cin >> ret;
  return ret;
}

} // namespace n91

#include <algorithm>
#include <iostream>
#include <utility>
#include <vector>

namespace n91 {

void main_() {
  /*
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  //*/
  const usize n = scan<usize>();
  const u64 m = scan<u64>();
  const usize v = scan<usize>();
  const usize p = scan<usize>();
  std::vector<u64> a(n);
  for (auto &e : a) {
    std::cin >> e;
  }
  std::sort(a.begin(), a.end(), std::greater<u64>());
  const auto is_ok = [&](const usize pos) {
    const u64 base = a[pos] + m;
    {
      usize cnt = 0;
      for (const auto e : a) {
        if (e > base) {
          cnt += 1;
        }
      }
      if (cnt >= p) {
        return false;
      }
    }
    u64 cur = 0;
    usize count = 0;
    for (const usize i : rep(0, n)) {
      if (i == pos)
        continue;
      if (count < p - 1) {
        count += 1;
        cur += m;
        continue;
      }
      if (a[i] <= base) {
        cur += std::min(base - a[i], m);
      }
    }
    if (cur >= m * (v - 1)) {
      return true;
    }

    return false;
  };
  usize ok = -static_cast<usize>(1), ng = n;
  while (ng - ok != 1) {
    const usize mid = (ok + ng) / 2;
    if (is_ok(mid)) {
      ok = mid;
    } else {
      ng = mid;
    }
  }
  std::cout << ng << std::endl;
}

} // namespace n91

int main() {
  n91::main_();
  return 0;
}


Measured memory_bytes: 1152