#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
typedef __int128_t lll;
template<typename T, bool ismin=true>
struct ConvexHullTrickMonotone{
	using P=pair<T, T>;
	deque<P> deq;
	ConvexHullTrickMonotone(){}
	void add(T a, T b){
		if(!ismin) a*=(-1), b*=(-1);
		if(deq.empty()){
			deq.push_back({a, b});
			return;
		}
		if(deq.back().first>=a){
			if(deq.back().first==a && deq.back().second<=b) return;
			while(deq.size()>1){
				T a1=deq.back().first, b1=deq.back().second;
				T a2=deq[deq.size()-2].first, b2=deq[deq.size()-2].second;
				if((b1-b2)*(a1-a)<(b-b1)*(a2-a1)) break;
				deq.pop_back();
			}
			deq.push_back({a, b});
		}else{
			while(deq.size()>1){
				T a1=deq.front().first, b1=deq.front().second;
				T a2=deq[1].first, b2=deq[1].second;
				if((b1-b2)*(a1-a)>(b-b1)*(a2-a1)) break;
				deq.pop_front();
			}
			deq.push_front({a, b});
		}
	}
	T get(T x, bool isinc){
		if(isinc){
			while(deq.size()>1){
				T a1=deq.front().first, b1=deq.front().second;
				T a2=deq[1].first, b2=deq[1].second;
				if(a1*x+b1<a2*x+b2) break;
				deq.pop_front();
			}
			T ret=deq.front().first*x+deq.front().second;
			if(ismin) return ret;
			else return -ret;
		}else{
			while(deq.size()>1){
				T a1=deq.back().first, b1=deq.back().second;
				T a2=deq[deq.size()-2].first, b2=deq[deq.size()-2].second;
				if(a1*x+b1<a2*x+b2) break;
				deq.pop_back();
			}
			T ret=deq.back().first*x+deq.back().second;
			if(ismin) return ret;
			else return -ret;
		}
	}
	void clear(){
		deq.clear();
	}
};
int main()
{
	int n;
	ll a, b, w;
	cin>>n>>a>>b>>w;
	ll d[300030]; d[n+1]=0;
	for(int i=1; i<=n; i++) cin>>d[i];
	ConvexHullTrickMonotone<lll> cht;
	cht.add(0, w);
	for(int i=1; i<=n+1; i++){
		ll dp=cht.get(i, true)+b*(i-1)*i/2+d[i]-a*(i-1);
		if(i==n+1){
			cout<<dp<<endl;
			return 0;
		}
		cht.add(-b*i, b*i*(i+1)/2+a*i+dp);
	}
 	return 0;
}