#include<bits/stdc++.h>
#define int long long
#define maxn 300005
using namespace std;
int n,A,B,W,d[maxn],dp[maxn],pre[maxn],ans=1e18;
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 head,tail,q[maxn];
signed main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n>>A>>B>>W;dp[0]=W;
	for(int i=1;i<=n;++i)dp[i]=1e18;
	for(int i=1;i<=n;++i)cin>>d[i];
	ans=W+n*(n+1)/2*B-n*A;
//	if(n<=3000){
//		for(int i=1;i<=n;++i){
//			for(int j=0;j<i;++j){
//				int res=(i-j-1)*(i-j);
//				dp[i]=min(dp[i],dp[j]+d[i]+(res)/2*B-(i-j-1)*A);
//			}
//			ans=min(ans,dp[i]+(n-i)*(n-i+1)/2*B-(n-i)*A);
//		}
//	}
//	else{
		for(int i=1;i<=n;++i){
			while(head<tail&&k(q[head],q[head+1])<=1.00*B*i)head++;
			int j=q[head];int res=(i-j-1)*(i-j);
			dp[i]=dp[j]+d[i]+(res)/2*B-(i-j-1)*A;
			while(head<tail&&k(q[tail],i)<=1.00*k(q[tail],q[tail-1]))tail--;
			q[++tail]=i;
			ans=min(ans,dp[i]+(n-i)*(n-i+1)/2*B-(n-i)*A);
		}
//	}
	cout<<min(ans,dp[n]);
	return 0;
}