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




typedef long double ld;
template<typename T> struct CHT {
	struct line {
		T slope, xterm;
		inline T get(const int x) const { return slope * x + xterm; }
	};
	deque<line> lines;
	inline ld area(const line& a, const line& b, const line& c) {
		ld ax = (b.slope - a.slope);
		ld bx = (c.xterm - a.xterm);
		ld ay = (c.slope - a.slope);
		ld by = (b.xterm - a.xterm);
		return ax * bx - ay * by;
	}
	inline bool cw(const line& a, const line& b, const line& c) {
		return area(a, b, c) < 0;
	}
	void add(T a, T b) {
		line l;
		l.slope = a, l.xterm = b;
		while (lines.size() > 1 && cw(lines[lines.size() - 2], lines[lines.size() - 1], l))
			lines.pop_back();
		if (lines.size() == 1) {
			if (lines.front().xterm > l.xterm)
				lines.push_back(l);
		}
		else lines.push_back(l);
	}
	T get(int x) {
		if (lines.empty())
			return 0;
		while (lines.size() > 1 && lines[0].get(x) > lines[1].get(x))
			lines.pop_front();
		return lines[0].get(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;
	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;
}