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





template<typename V> struct ConvexHull {
	deque<pair<V, V>> Q;
	int cmptype = 0; // 0-min 1-max
	V calc(pair<V, V> p, V x) {
		return p.first*x + p.second;
	}
	int dodo(pair<V, V> A, pair<V, V> B, pair<V, V> C) { // max or min
		return cmptype ^ ((B.second - C.second)*(B.first - A.first) <= (A.second - B.second)*(C.first - B.first));
	}
	void add(V a, V b) { // add ax+b
		Q.push_front({ a,b });
		while (Q.size() >= 3 && !dodo(Q[0], Q[1], Q[2]))
			Q[1] = Q[0], Q.pop_front();
	}
	V get(V x) {
		int L = -1, R = Q.size() - 1;
		while (R - L>1) {
			int M = (L + R) / 2;
			((cmptype ^ ((calc(Q[M], x) >= calc(Q[M + 1], x)))) ? L : R) = M;
		}
		return calc(Q[R], 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]);

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

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

	cout << ans << endl;
}