#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

using int128=__int128;
 
ostream &operator<<(ostream &os,const __int128 n){
    if(n==0){
        os<<0;
        return os;
    }
    __int128 num=n;
    bool neg=false;
    if(num<0)neg=true,num=-num;
    string res="";
    while(num>0){
        res.push_back('0'+num%10);
        num/=10;
    }
    if(neg) res.push_back('-');
    reverse(begin(res),end(res));
    os<<res;
    return os;
}
 
istream &operator>>(istream &is,__int128 &n){
    string s;
    is>>s;
    int idx=0;
    bool neg=false;
    if(s[0]=='-')neg=true,idx++;
    n=0;
    for(;idx<(int)s.size();idx++){
        n=10*n+s[idx]-'0';
    }
    if(neg) n=-n;
    return is;
}
 
__int128 abs(__int128 x){
    return x<0?-x:x;
}
 
__int128 gcd(__int128 a,__int128 b){
    if(a==0) return b;
    if(b==0) return a;
    return b>0?gcd(b,a%b):a;
}
 



template<typename Monoid>
struct SegmentTree{
    using F=function<Monoid(Monoid,Monoid)>;
    int sz;
    vector<Monoid> seg;
    const F f;
    const Monoid gen;
    SegmentTree(int n,const F f,const Monoid &gen):f(f),gen(gen){
        sz=1;
        while(sz<n)sz<<=1;
        seg.assign(2*sz,gen);
    }
    void set(int k,const Monoid &x){
        seg[k+sz]=x;
    }
    void build(){
        for(int k=sz-1;k>0;k--) seg[k]=f(seg[2*k],seg[2*k+1]);
    }
    void update(int k,const Monoid &x){
        k+=sz;
        seg[k]=x;
        while(k>>=1) seg[k]=f(seg[2*k],seg[2*k+1]);
    }
   // [a,b)
    Monoid query(int a,int b){
        Monoid L=gen,R=gen;
        for(a+=sz,b+=sz;a<b;a>>=1,b>>=1){
            if(a&1) L=f(L,seg[a++]);
            if(b&1) R=f(seg[--b],R);
        }
        return f(L,R);
    }
    Monoid operator[](const int &k)const {
       return seg[k+sz];
    }
};
int128 f(int128 a,int128 b){
    return a+b;
}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int128 n,k,x,y;cin>>n>>k>>x>>y;
    vector<int128> a(n);
    rep(i,n){
        cin>>a[i];
        a[i]--;
        a[i]=(a[i]+k-1)/k;
    }
    sort(ALL(a));
    // debug(a);

    SegmentTree<int128> seg(n,f,0);
    rep(i,n) seg.set(i,a[i]);
    seg.build();

    int128 ans=1001002003004005006;
    for(int i=0;i<=n;i++){
        int128 cost=0;
        int128 b=0;
        if(i>0) b=a[i-1],cost+=a[i-1]*y;
        
        cost+=(seg.query(i,n)-(n-i)*b)*x;
        // cout<<i<<" : "<<cost<<endl;
        chmin(ans,cost);
    }
    cout<<ans<<endl;
    return 0;
}