#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
#define F first
#define S second
ll n,A,B,W,d[300005],dp[300005];
P dq[300005];
bool check(P a,P b,P c){return (a.F-b.F)*(b.S-c.S)>=(a.S-b.S)*(b.F-c.F);}
int main(void){
	scanf("%lld%lld%lld%lld",&n,&A,&B,&W);
	for(int i=1;i<=n;i++)scanf("%lld",d+i);
	dp[0]=W;
	ll l=0,r=0;
	for(ll i=1;i<=n+1;i++){
		P p=P(-B*i,dp[i-1]+B*i*(i-1)/2+i*A);
		while(r-2>=l&&check(dq[r-2],dq[r-1],p))r--;
		dq[r++]=p;
		while(l+1<r&&dq[l+1].F*i+dq[l+1].S<=dq[l].F*i+dq[l].S)l++;
		dp[i]=dq[l].F*i+dq[l].S+d[i]-A*i+B*i*(i+1)/2;
	}	
	printf("%lld\n",dp[n+1]);
}