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