#include<bits/stdc++.h>
#include<unordered_set>
#include<unordered_map>
using namespace std;
#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
typedef long long ll;
typedef pair<ll,ll> pll;
typedef long double ld;
const ll inf=1e9+7;
const ll mod=1e9+7;
signed main(){
    ll n,k,x,y;cin>>n>>k>>x>>y;
    vector<ll>a(n);
    rep(i,n){
        cin>>a[i];
        a[i]--;
        if(a[i]==0){
            continue;
        }else{
            a[i]=(a[i]-1)/k+1;
        }
    }
    ll l=-1,r=inf;
    while(r-l>1){
        ll mid=(r+l)/2;
        ll cnt=0;
        rep(i,n){
            cnt+=max(0LL,a[i]-mid);
        }
        ll cn=0;
        rep(i,n){
            cn+=max(0LL,a[i]-mid-1);
        }
        if(cnt*x+mid*y<=cn*x+(mid+1)*y){
            r=mid;
        }else{
            l=mid;
        }
    }
    ll cnt=0;
    rep(i,n){
        cnt+=max(0LL,a[i]-r);
    }
    cout<<r*y+cnt*x<<endl;
}