#include<bits/stdc++.h>
#define int __int128
using namespace std;
using ld=long double;
inline int read()
{
    int x=0,f=1;
    char ch=getchar();
    while(!isdigit(ch))
	{
        if(ch=='-')f=-1;
        ch=getchar();
    }
    while(isdigit(ch))
	{
        x=(x<<1)+(x<<3)+(ch^48);
        ch=getchar();
    }
    return x*f;
}
inline void write(int x)
{
    if(x<0)
	{
        putchar('-');
        write(-x);
        return;
    }
    if(x>9)write(x/10);
    putchar(x%10+48);
    return;
}
int n,a,b,w,d[1000100],f[1000100],q[1000100],hd=1,tl=1;
ld Y(int i){return f[i]+(i*(i+1))*b/2+i*a;}
ld X(int i){return 1.0*i;}
ld k(int i1,int i2){return (Y(i2)-Y(i1))/(X(i2)-X(i1));}
signed main()
{
	memset(f,0x3f,sizeof f);
	n=read(),a=read(),b=read(),w=read();
	for(int i=1;i<=n;++i)d[i]=read();
	f[0]=w;
	for(int i=1;i<=n;++i)
	{
		while(hd<tl&&k(q[hd],q[hd+1])<=i*b)++hd;
		f[i]=f[q[hd]]-(i-q[hd]-1)*a+d[i]+(i-q[hd]-1)*(i-q[hd])*b/2;
		while(hd<tl&&k(q[tl],i)<=k(q[tl],q[tl-1]))--tl;
		q[++tl]=i;
	}
	int ans=2e18;
	for(int i=n;~i;--i)ans=min(ans,f[i]-(n-i)*a+(n-i+1)*(n-i)*b/2);
	write(ans);
	return 0;
}