#include <algorithm>
#include <bitset>
#include <cassert>
#include <complex>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <typeinfo>
#include <utility>
#include <vector>
#include <array>
#include <chrono>
#include <random>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
#define VAR(type, ...)type __VA_ARGS__;Scan(__VA_ARGS__);
template<typename T> void Scan(T& t) { std::cin >> t; }
template<typename First, typename...Rest>void Scan(First& first, Rest&...rest) { std::cin >> first; Scan(rest...); }
#define OUT(d) std::cout<<d;
#define FOUT(n, d) std::cout<<std::fixed<<std::setprecision(n)<<d;
#define SOUT(n, c, d) std::cout<<std::setw(n)<<std::setfill(c)<<d;
#define SP std::cout<<" ";
#define TAB std::cout<<"\t";
#define BR std::cout<<"\n";
#define ENDL std::cout<<std::endl;
#define FLUSH std::cout<<std::flush;
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
#define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& r:c)for(auto& i:r)std::cin>>i;
#define ALL(a) (a).begin(),(a).end()
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define RFOR(i, a, b) for(int i=(b)-1;i>=(a);--i)
#define REP(i, n) for(int i=0;i<int(n);++i)
#define RREP(i, n) for(int i=(n)-1;i>=0;--i)
#define PAIR std::pair<int, int>
#define IN(a, x, b) (a<=x && x<=b)
#define IN2(a0, y, a1, b0, x, b1) (a0<=y && y<a1 && b0<=x && x<b1)
#define SHOW(d) {std::cout << #d << "\t:" << d << "\n";}
#define SHOWVECTOR(v) {std::cout << #v << "\t:";for(const auto& i : v){std::cout << i << " ";}std::cout << "\n";}
#define SHOWVECTOR2(v) {std::cout << #v << "\t:\n";for(const auto& i : v){for(const auto& j : i){std::cout << j << " ";}std::cout << "\n";}}
#define SHOWPAIRVECTOR2(v) {std::cout << #v << "\t:\n";for(const auto& i : v){for(const auto& j : i){std::cout<<'('<<j.first<<", "<<j.second<<") ";}std::cout << "\n";}}
#define SHOWPAIRVECTOR(v) {for(const auto& i:v){std::cout<<'('<<i.first<<", "<<i.second<<") ";}std::cout<<"\n";}
#define CHECKTIME(state) {auto start=std::chrono::system_clock::now();state();auto end=std::chrono::system_clock::now();auto res=std::chrono::duration_cast<std::chrono::nanoseconds>(end-start).count();std::cerr<<"[Time:"<<res<<"ns  ("<<res/(1.0e9)<<"s)]\n";}
#define SHOWQUEUE(a) {std::queue<decltype(a.front())> tmp(a);std::cout << #a << "\t:";for(int i=0; i<static_cast<int>(a.size()); ++i){std::cout << tmp.front() << "\n";tmp.pop();}std::cout << "\n";}

//#define int ll
using ll = long long;
constexpr int INFINT = 1 << 30;
constexpr ll INFLL = 1LL << 60;
constexpr double EPS = 0.0000001;
constexpr int MOD = 1000000007;

// dp[i] := i番目にドーナツを食べたときの体重の変化量の最小値
ll dp[300005];
int deq[300005];

signed main() {
	INIT;
	VAR(ll, n, a, b, w);
	VEC(int, d, n);

	// 直線y=-G[t]*x+F[i]に対してx=iだった時の値y
	auto f = [&](ll t, ll i) ->ll {
		return  -(t*b)*i + (dp[t] + t*a + (t*t + t) / 2 * b);
	};

	// 直線f1, f2, f3のうちf2がいつか最小値を取る可能性があるかを判定する
	auto check = [&](ll f1, ll f2, ll f3) {
		ll a1 = -(f1*b), b1 = (dp[f1] + f1*a + (f1*f1 + f1) / 2 * b);
		ll a2 = -(f2*b), b2 = (dp[f2] + f2*a + (f2*f2 + f2) / 2 * b);
		ll a3 = -(f3*b), b3 = (dp[f3] + f3*a + (f3*f3 + f3) / 2 * b);
		return (a2 - a1)*(b3 - b2) >= (b2 - b1)*(a3 - a2);
	};
	
	deq[0] = 0;
	int h = 0, t = 1;

	dp[0] = 0;
	FOR(i, 1, n + 1) {
		// 先頭が最小値を取らなければ取り除く
		while (h + 1 < t && f(deq[h], i) >= f(deq[h + 1], i)) ++h;

		dp[i] = f(deq[h], i) - a*(i - 1) + (i*i - i) / 2 * b + d[i - 1];

		// 末尾から最小値を取る可能性がなくなったものを取り除く
		while (h + 1 < t && check(deq[t - 2], deq[t - 1], i)) --t;
		// 直線を追加
		deq[t++] = i;
	}
	ll ans = INFLL;
	REP(i, n + 1) {
		ans = std::min(ans, dp[i] - a*(n - i) + (n - i)*(n - i + 1)/2*b);
	}
	OUT(ans+w)BR;
	return 0;
}