#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];
long double Y(int i){
	return 1.0*(dp[i]+i*a+1.0*b*(i*i+i)/2);
}
long double X(int i){
	return 1.0*i;
}
long double K(int j1,int j2){
	return 1.0*(Y(j1)-Y(j2))/(X(j1)-X(j2));
}
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++)dp[i]=1e18;
	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 && 1.0*(Y(q[head])-Y(q[head+1]))>=i*b*(X(q[head])-X(q[head+1])))head++;
//		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]+b*(i-j-1)*(i-j)/2;
//		while(head<tail && K(q[tail],i)<=K(q[tail],q[tail-1]) )tail--;
		while(head<tail && (Y(q[tail])-Y(i))*(X(q[tail])-X(q[tail-1]))<=(Y(q[tail])-Y(q[tail-1]))*(X(q[tail])-X(i)))tail--;
		q[++tail]=i;
	}
	
	int ans=1e18;
	for(int i=n;i>=0;i--){
		ans=min(ans,dp[i]-(n-i)*a+b*(n-i+1)*(n-i)/2);
	}
	cout<<ans;
	return 0;
}