#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
#include <random>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<int, ll> i_ll;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N; ll A, B, W;
	cin >> N >> A >> B >> W;
	vector<ll> D(N);
	for (ll& x: D) scanf("%lld", &x);
	N++; D.push_back(0);
	int M = 1;
	vector<i_ll> p; p.push_back(i_ll(0, 0));
	ll ans;
	for (int i = 0; i < N; i++) {
		ll mi = LLONG_MAX;
		for (i_ll z: p) {
			int j = z.first; ll x = z.second;
			ll k = i - j;
			ll _x = x + k*(k+1)/2 * B - k * A + D[i];
			mi = min(mi, _x);
		}
		i_ll _p(i + 1, mi);
		for (; M >= 2 && (double)(p[M - 1].second - p[M - 2].second) / (p[M - 1].first - p[M - 2].first) <= (double)(_p.second - p[M - 1].second) / (_p.first - p[M - 1].first + EPS); M--, p.pop_back());
		p.push_back(_p);
		ans = mi;
	}
	cout << W + ans << endl;
}