Problem:
Score : 700 points

Problem Statement

N problems are proposed for an upcoming contest. Problem i has an initial integer score of A_i points.

M judges are about to vote for problems they like. Each judge will choose exactly V problems, independently from the other judges,
and increase the score of each chosen problem by 1.

After all M judges cast their vote, the problems will be sorted in non-increasing order of score, and the first P problems will be chosen for the problemset.
Problems with the same score can be ordered arbitrarily, this order is decided by the chief judge.

How many problems out of the given N have a chance to be chosen for the problemset?

Constraints

2 \le N \le 10^5

1 \le M \le 10^9

1 \le V \le N - 1

1 \le P \le N - 1

0 \le A_i \le 10^9

Input

Input is given from Standard Input in the following format:

N M V P
A_1 A_2 ... A_N

Output

Print the number of problems that have a chance to be chosen for the problemset.

Sample Input 1

6 1 2 2
2 1 1 3 0 2

Sample Output 1

5

If the only judge votes for problems 2 and 5, the scores will be 2 2 1 3 1 2.
The problemset will consist of problem 4 and one of problems 1, 2, or 6.

If the only judge votes for problems 3 and 4, the scores will be 2 1 2 4 0 2.
The problemset will consist of problem 4 and one of problems 1, 3, or 6.

Thus, problems 1, 2, 3, 4, and 6 have a chance to be chosen for the problemset. On the contrary, there is no way for problem 5 to be chosen.

Sample Input 2

6 1 5 2
2 1 1 3 0 2

Sample Output 2

3

Only problems 1, 4, and 6 have a chance to be chosen.

Sample Input 3

10 4 8 5
7 2 3 6 1 6 5 4 6 5

Sample Output 3

8

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include "bits/stdc++.h"
#define _USE_MATH_DEFINES
#include <math.h>
 
using namespace std;
 
using LL = long long;
using VLL = std::vector<LL>;
using VVLL = std::vector<VLL>;
using VVVLL = std::vector<VVLL>;
using LD = long double;
using VLD = std::vector<LD>;
using VVLD = std::vector<VLD>;
using VVVLD = std::vector<VVLD>;
using BL = bool;
using VBL = std::vector<BL>;
using VVBL = std::vector<VBL>;
using VVVBL = std::vector<VVBL>;


template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }

//template<class T=LL> inline vector<T> cinv(LL N){ vector<T> v(N); REP(i, N)cin>>v[i]; return move(v);}
//template<class T=LL> inline vector<T> cinv(LL N){ vector<T> v(N); REP(i, N)cin>>v[i]; return move(v);}
#define REP(i,n) for(LL (i)=0;(i)<(n);(i)++)
#define REPM(i,n,m) for(LL (i)=m;(i)<(n);(i)++)
#define ALL(v) v.begin(), v.end()
#define PRINTLN(v) {LL i=0; for(auto (a): v ){   cerr <<i << " : "<<  a << endl; i++;}}
//#define PRLLSP(v) for(auto (a): v ) {cerr << a << " ";} cerr << endl

template<class T> 
void PRINTSP(vector<T> v, size_t w=3){
  for(auto (a): v ) {cerr <<setw(w)<< a << " ";} cerr << endl;
} 

template<typename TTT>
vector<LL> arg_sort(vector<TTT> A, bool ascend = true) {
  vector<LL> index(A.size());
  iota(index.begin(), index.end(), 0);
  if (ascend) {
    std::sort(index.begin(), index.end(), [&A](TTT i1, TTT i2) {
      return A[i1] < A[i2];
      });
  }
  else {
    std::sort(index.begin(), index.end(), [&A](TTT i1, TTT i2) {
      return A[i1] > A[i2];
      });
  }

  return index;
}

struct UinonFindTree {
private:
  vector<LL> UFT;
public:
  UinonFindTree(LL N) {
    UFT.resize(N);
    for (LL i = 0; i < N; i++) {
      UFT[i] = -1; 
    }
  }

  LL root(LL i) { 
    if (UFT[i] < 0) {
      return i;
    }
    else {
      LL j = root(UFT[i]);
      UFT[i] = j;
      return j;
    }
  }

  bool same(LL i, LL j) {
    return (root(i) == root(j));
  }

  void unite(LL i, LL j)
  {
    LL root_i = root(i);
    LL root_j = root(j);
    if (root_i != root_j) {
      if (size(root_i) < size(root_j)) {
        swap(root_i, root_j);
      }
      UFT[root_i] += UFT[root_j];
      UFT[root_j] = root_i;
    }
  }

  LL size(LL i) {
    return -UFT[root(i)];
  }

  LL get_root_num() {
    set<LL> roots;
    for (LL i = 0; i < UFT.size(); ++i) {
      roots.insert(root(i));
    }
    return (LL)roots.size();
  }

  map<LL, vector<LL>> get_root_child() {
    map<LL, vector<LL>> a;
    for (LL i = 0; i < UFT.size(); ++i) {
      LL j = root(i);
      a[j].push_back(i);
    }
    return a;
  }

  void prLL() { 
    for (LL i = 0; i < UFT.size(); ++i) {
      cerr << root(i) << " ";
    }
    cerr << endl;
  }
};



#define cmax(a,b) {if(a<b){a=b;}}
#define cmin(a,b) {if(a>b){a=b;}}
#define EACH(a,A) for(auto a: A)
//#define cmax(a,b) a = (a>b ? a:b)
//#define cmin(a,b) a = (a<b ? a:b) 
//cin,cout高速化のおまじない＋桁数指定
inline VLL cinvll(LL N, LL minus = 0){
  VLL A(N);
  REP(i,N){
    cin >> A[i];
    A[i] -= minus;
  }
  return move(A);
}
inline VVLL zerosll(LL H, LL W, LL val=0){
  VVLL A(H,VLL(W,val));
  return move(A);
}
struct Fast{
	Fast(){
		cin.tie(0);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(std::numeric_limits<double>::max_digits10);
	}
} fast;

#if 0 
LL GCD(LL m, LL n) {

  if (m < n) {
    swap(m, n);
  }

  while (n != 0) {
    LL n_new = m % n;
    m = n;
    n = n_new;
  }

  return m;

}

VLL B;
VVLL T;
LL cnt=0;
void dfs(LL me,LL oya){

  for(LL i=0;i<T[me].size();i++){
    LL ko = T[me][i];
    if(ko==oya){
      continue;
    }
    cnt += min(B[me],B[ko]);
    dfs(ko,me);
  }

}
#endif 

VLL A;
VLL I;
LL N,M,V,P;
LL TH;
bool isOK(LL index) {
  LD X = A[index]+M;
  //if(A[index]+M>=TH){
  //  return true;
  //}
  //LL nokori = V-(P-1)-index-1;
  LL nokori = V-(P-1)-index-1;
  if (nokori<=0){
    if(X>=TH){
      return true;
    }
    else{
      return false;
    }
  }
  LL cnt=0;
  LL st=index+1;
  LL en=N-P;  
  for(LL i=st;i<en;i++){
    cnt += A[i];
  }
  /*
  LL cnt=0;
  LL st=index+1;
  LL en=N-(P-1);  
  for(LL i=st;i<en;i++){
    cnt += A[i];
  }
  */
  /*
  cerr << "TH " << TH << endl;
  cerr << "index=" << index<<endl;;
  cerr << "A[index]=" << A[index]<<endl;;
  cerr << "A[index]+M=" << A[index]+M<<endl;;
  cerr << "Nokori=" << nokori << endl;
  cerr << "Nokori*M=" << nokori*M << endl;
  cerr << "cnt=" << cnt << endl;
  cerr << "en-st=" << en-st << endl;
  cerr << "cnt2=" << cnt << endl;
*/

  cnt += nokori*M;
  LD val = (cnt)/(LD)(en-st);
  //cerr << "X=" << X << endl;
  //cerr << "val=" << val << endl;
  //if(X >=val){
  if(X*(en-st-1)>=cnt){
    //cerr << "true"<< endl;
    //cerr << "------------" << endl;
    return true;
  }
  else{
    //cerr << "false"<< endl;
    //cerr << "------------" << endl;
    return false;
  }
}
LL binary_search() {
    LL left = -1; //「index = 0」が条件を満たすこともあるので、初期値は -1
    LL right = (LL)A.size(); // 「index = a.size()-1」が条件を満たさないこともあるので、初期値は a.size()

    /* どんな二分探索でもここの書き方を変えずにできる！ */
    while (right - left > 1) {
        LL mid = left + (right - left) / 2;

        if (isOK(mid)) right = mid;
        else left = mid;
    }

    /* left は条件を満たさない最大の値、right は条件を満たす最小の値になっている */
    return right;
}
void func(){
  cin >>N>>M>>V>>P;
  A = cinvll(N);
  //I.resize(N);
  sort(ALL(A));
  //PRINTSP(A);
  TH = A[N-P];
  LL index = binary_search();
  cout<< N-index;
  //isOK(0);
}


int main()
{
  func();
  return 0;
}