#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)




template<typename T> struct CHT { // by satanic
	typedef pair<T, T> pa;
	vector<pa> lines; bool mono; function<bool(T l, T r)> comp;
	// クエリが単調ならf = true
	CHT(bool f = false, function<bool(T l, T r)> co = [](T l, T r) {return l >= r; }) :mono(f), comp(co) { };

	bool check(pa l1, pa l2, pa l3) {
		if (l1 < l3) std::swap(l1, l3);
		return (l3.second - l2.second) * (l2.first - l1.first) >= (l2.second - l1.second) * (l3.first - l2.first);
	}

	void add(T a, T b) { // y=ax+b
		pa line(a, b);
		while (lines.size() >= 2 && check(*(lines.end() - 2), lines.back(), line)) lines.pop_back();
		lines.emplace_back(line);
	}

	T f(int i, T x) { return lines[i].first * x + lines[i].second; }
	T f(pa line, T x) { return line.first * x + line.second; }

	T get(T x) {
		if (mono) {
			static int head = 0;
			while (lines.size() - head >= 2 && comp(f(head, x), f(head + 1, x))) ++head;
			return f(head, x);
		} else {
			int low = -1, high = lines.size() - 1;
			while (high - low > 1) {
				int mid = (high + low) / 2;
				(comp(f(mid, x), f(mid + 1, x)) ? low : high) = mid;
			}
			return f(high, x);
		}
	}
};
//-----------------------------------------------------------------------------------
typedef long long ll;
#define INF 1LL<<60
int N, A, B, W;
int D[301010];
//-----------------------------------------------------------------------------------
ll dp[301010];
int main() {
	cin >> N >> A >> B >> W;
	rep(i, 0, N) scanf("%d", &D[i]);

	/* Naive
	dp[0] = W;
	rep(i, 1, N + 1) {
		dp[i] = INF;
		rep(j, 0, i) {
			ll w = dp[j];
			w -= 1LL * A * (i - j - 1);
			w += 1LL * (i - j - 1) * (i - j) / 2 * B;
			dp[i] = min(dp[i], w);
		}
		dp[i] += D[i - 1];
	}
	*/

	// Optimized
	CHT<ll> cht(true);
	dp[0] = W;
	cht.add(0, W);
	rep(i, 1, N + 1) {
		dp[i] = cht.get(i) - 1LL * (i - 1) * A + (1LL * (i - 1) * i) / 2 * B + D[i - 1];
		cht.add(-1LL * B * i, dp[i] + 1LL * A * i + (1LL * i * i + i) / 2 * B);
	}

	ll ans = INF;
	rep(i, 0, N + 1) {
		ll w = dp[i];
		int n = N - i;
		w -= 1LL * A * n;
		w += 1LL * n * (n + 1) / 2 * B;
		ans = min(ans, w);
	}

	cout << ans << endl;
}