#include<iostream>
#include<deque>
using namespace std;
int N;
long A,B,W,D[3<<17];
long b[3<<17],dp[3<<17];
long f(int id,int x){return -id*B*x+b[id];}
bool check(int i,int j,int k)
{
	if(B==0)return true;
	return (j-i)*(b[k]-b[j])<=(b[j]-b[i])*(k-j);
}
main()
{
	cin>>N>>A>>B>>W;
	for(int i=0;i<N;i++)cin>>D[i];
	dp[0]=W;
	deque<int>P;
	for(long i=0;i<N;i++)
	{
		b[i]=dp[i]+A*i+i*(i+1)/2*B;
		while(P.size()>=2&&check(P[P.size()-2],P.back(),i))P.pop_back();
		P.push_back(i);
		while(P.size()>=2&&f(P[1],i+1)<=f(P[0],i+1))P.pop_front();
		dp[i+1]=f(P[0],i+1)+D[i]-A*i+i*(i+1)/2*B;
	}
	long ans=9e18;
	for(long i=0;i<=N;i++)ans=min(ans,dp[i]-A*(N-i)+(N-i)*(N-i+1)/2*B);
	cout<<ans<<endl;
}