#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long n,k,x,y;
    cin >> n >> k >> x >> y;
    int sum = 0;
    vector<long long>ans;
    for(int i=0; i<n; i++)
    {
        int x;
        cin>>x;
        x--;
        int a = x/k;
        if(x%k)a++;
        ans.push_back(a);
        //cout<<a<<" ";
        sum+=a;
    }
    //cout<<endl;
    sort(ans.begin(),ans.end());
    if(sum*x<=y)cout<<sum*x<<endl;
    else
    {
       //cout<<ans[ans.size()-1]*y<<endl;
       long long res = sum*x;
       res = min(res, ans[ans.size()-1]*y);
       long long picked = 0;
       for(int i=0; i<n; i++)
       {
           picked += ans[i];
           long long baki = sum - picked;
           long long next = baki - (n-(i+1))*ans[i];
           //cout<<ans[i]<<" "<<baki<<" "<<next<<endl;
           //cout<<y*ans[i]<<" "<<x*next<<endl;
           res = min(res,y*ans[i]+x*next);
       }
       cout<<res<<endl;
    }
}