#include<bits/stdc++.h>
using namespace std;
int d[300005],q[300005];
long long f[300005];
int hd=1,tl=0;
bool ok(int x,int y,int z){
	return (__int128)(f[y]-f[x])*(z-y)>=(__int128)(f[z]-f[y])*(y-x);
}
bool test(int x,int y,long long z){
	return f[y]-f[x]<=(__int128)(y-x)*z;
}
void add(int x){
	while(tl>=hd+1&&ok(q[tl-1],q[tl],x))--tl;
	q[++tl]=x;
}
int main(){
	int n,a,b,w;
	scanf("%d%d%d%d",&n,&a,&b,&w);
	for(int i=1;i<=n;++i)scanf("%d",&d[i]);
	memset(f,63,sizeof(f));
	f[0]=w;
	for(int i=1;i<=n+1;++i){
		long long sz=1ll*i*a+1ll*i*(i-1)/2*b;
		f[i-1]+=sz;
		add(i-1);
		while(tl>=hd+1&&test(q[hd],q[hd+1],1ll*i*b))++hd;
		int j=q[hd];f[i]=f[j]-1ll*i*j*b;
		long long zs=d[i]-1ll*i*a+1ll*i*(i-1)/2*b;
		f[i]+=zs;
	}
	printf("%lld\n",f[n+1]);
	return 0;
}