#include <iostream>
#include <iomanip>
#include <algorithm>
#include <deque>
using namespace std;

#define Inf 1e15
#define maxn 300010

long long d[maxn];
long long dp[maxn][2]; // dp[i][0]: sleep at i day, dp[i][1]: read at i day

struct line { // y = mx + b
	long long m; // slope
	long long b; // intercept
	line(long long m, long long b): m(m), b(b) {}
};

long long foo(line l, long long i, long long a, long long b) { // return dp[i][1] from line l(j)
	return l.m * i + l.b + b * i * (i + 1) / 2 - a * i;
}

double vertex(line l1, line l2) { // the intersection of l1 and l2
	return 1.0 * (l2.b - l1.b) / (l1.m - l2.m);
}

// reamin: w
// days: n
// study 1 day: -a
// study for x days: + x * b
// sleep in i day: + d[i]

int main() {
	long long n, a, b, w;
	cin >> n >> a >> b >> w;
	for (int i = 1; i <= n; i++)
		cin >> d[i];
	dp[0][0] = dp[0][1] = w;
	deque<line> dq;
	dq.push_front(line(0, w)); // sine dp[j][0] = w
	for (long long i = 1; i <= n; i++) {
		dp[i][0] = min(dp[i - 1][0], dp[i - 1][1]) + d[i]; // sleep
		// consider the value of dp[i][1] by subtituting i into dq[0]
		while (dq.size() > 1 && (foo(dq[1], i, a, b) < foo(dq[0], i, a, b)))
			dq.pop_front(); // we no longer need dq[0], pop out
		dp[i][1] = foo(dq[0], i, a, b);
		// cout << dp[i][0] << " " << dp[i][1] << " " << dq.size() << '\n';
		// add line "i" into dq
		line tmp = line(0, 0);
		tmp.m = -1 * i * b; // since this line will be treat as j in the future, the slope's j = i now
		tmp.b = dp[i][0] + b * i * (i - 1) / 2 + i * a;
		while (dq.size() >= 2 && (vertex(dq[dq.size() - 1], dq[dq.size() - 2]) > vertex(tmp, dq[dq.size() - 2])))
			dq.pop_back();
		dq.push_back(tmp);
	}
	cout << min(dp[n][1], dp[n][0]) << '\n';
	return 0;
}