#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

template<class T>bool chmax(T &a, const T &b) { return (a<b)?(a=b,1):0;}
template<class T>bool chmin(T &a, const T &b) { return (b<a)?(a=b,1):0;}

using namespace std;
using ll=long long;
const ll inf=1LL<<58;

ll d[300010];
ll ca[300010],cb[300010];
ll dp[300010];

deque<int> deq;

inline bool check(int i,int j,int k){ return (ca[j]-ca[i])*(cb[k]-cb[j])>= (cb[j]-cb[i])*(ca[k]-ca[j]);}
inline ll f(int idx,int i){ return -ca[idx]*i+cb[idx];}

int main(void){
	int n,a,b,w;
	cin >> n >> a >> b >> w;
	rep(i,n) cin >> d[i];

	dp[0]=w,ca[0]=0,cb[0]=dp[0];
	deq.push_back(0);

	rep(i,1,n+1){
		while(deq.size()>=2 && f(deq[0],i) >= f(deq[1],i)) deq.pop_front();
		int idx=deq.front();
		dp[i]=d[i-1]-(i-1)*a+(i-1)*i/2*b+f(idx,i);		
		ca[i]=b*i,cb[i]=dp[i]+i*a+i*(i+1)/2*b;
		const int m=deq.size();
		while(deq.size()>=2 && check(deq[m-2],deq[m-1],i)) deq.pop_back();
		deq.push_back(i);
	}

	ll ans=inf;
	rep(i,n+1){
	    ll e=n-i;
        chmin(ans,dp[i]+b*e*(e+1)/2-a*e);
    }
    cout << ans << endl;
	return 0;
}