#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read()
{
	register int x=0,f=0;register char c=getchar();
	while(c<'0'||c>'9')f=(c=='-'),c=getchar();
	while(c>='0'&&c<='9')x=(x<<3)+(x<<1)+(c&15),c=getchar();
	return f?-x:x;
}
const int MAXN=1e6;
int n,a,b,w,d[MAXN],dp[MAXN];
double Y(int i){
	double s=dp[i]+i*i*0.5*b+b*i*0.5+i*a;
	return s*1.000;
}
int X(int i){
	return 1.0*i;
}
//long double K(int j1,int j2){
//	return (long double)1.0*(Y(j1)-Y(j2))/(X(j1)-X(j2));
//}
//inline long double Y(int i){
//	double s=dp[i]+b*i*i*0.5+b*i*0.5+i*a;
//	return s*1.000;
//}
//inline long double X(int i){return i*1.00;}
inline long double K(int i,int j){return (Y(i)-Y(j))*1.00/(X(i)-X(j));}
int q[MAXN],head,tail;
signed main()
{
//	freopen("chips.in","r",stdin);
//	freopen("chips.out","w",stdout);
	memset(dp,0x3f,sizeof dp);
	n=read();a=read();b=read();w=read();
	for(int i=1;i<=n;i++)d[i]=read();
	dp[0]=w;
	head=1;tail=1;q[1]=0;
	for(int i=1;i<=n;i++){
		while(head<tail && K(q[head],q[head+1])<=1.0*i*b)head++;
		int j=q[head];
		dp[i]=dp[j]-(i-j-1)*a+d[i]+(i-j-1)*(i-j)/2*b;
		while(head<tail && K(q[tail],i)<=K(q[tail],q[tail-1]) )tail--;
		q[++tail]=i;
	}
	
	int ans=1e18;
	for(int i=n;i>=0;i--){
		ans=min(ans,dp[i]-(n-i)*a+(n-i+1)*(n-i)/2*b);
	}
	cout<<ans;
	return 0;
}