#define PROBLEM "https://yukicoder.me/problems/no/409"

#include <iostream>
#include <memory>
#include <vector>
#include <numeric>

// X_MAX: ax+bであるxとして取りうる最大値
template<long long X_MAX, class T = long long>
class DynamicLiChaoTree {
    constexpr static T INF = 2e18;

    class Line {
        T a, b;
    public:
        Line(const T& a, const T& b) :a(a), b(b) {}
        Line() :Line(0, INF) {}
        Line(const Line& other) noexcept :Line(other.a, other.b) {}
        Line(Line&& other) noexcept :Line(other) {}
        Line& operator=(Line&& other) noexcept {
            if(this != &other) { a = other.a; b = other.b; }
            return *this;
        }
        auto operator<(const Line& line)const { return a < line.a; }
        auto operator>(const Line& line)const { return line.operator<(*this); }

        auto f(const T& x)const { return a * x + b; }
        auto debug()const { std::cerr << "(" << a << " " << b << ")" << std::endl; }
    };

    struct Node {
        Line line;
        std::unique_ptr<Node> left;
        std::unique_ptr<Node> right;

        Node(const Line& line) :line(line) {}
        auto f(const T& x)const { return line.f(x); }
    };

    std::unique_ptr<Node> m_root;

    auto add(std::unique_ptr<Node>& node, Line&& line, long long l, long long r) {
        if(!node) { node = std::make_unique<Node>(line); return; }

        auto m = (l + r) / 2;
        if(line.f(m) < node->f(m)) { std::swap(node->line, line); }
        if(l + 1 == r) { return; }
        if(line > node->line) {
            add(node->left, std::move(line), l, m);
        } else if(line < node->line) {
            add(node->right, std::move(line), m, r);
        }
    }

    auto query(const std::unique_ptr<Node>& node, const T& x, long long l, long long r) const {
        if(!node) { return Line().f(x); }
        auto m = (l + r) / 2;
        return std::min(
            node->f(x),
            (x < m) ? query(node->left, x, l, m) : query(node->right, x, m, r)
        );
    }
public:
    DynamicLiChaoTree() {}

    auto add(const T& a, const T& b) { add(m_root, Line(a, b), -X_MAX, X_MAX); }
    auto add(const std::pair<T, T>& line) { add(line.first, line.second); }
    auto query(const T& x) const { return query(m_root, x, -X_MAX, X_MAX); }

    auto debug(const std::unique_ptr<Node>& node, int size)const {
        if(size == 0) { std::cerr << "-- li chao tree --" << std::endl; }
        if(!node) { return; }
        for(int i = 0; i < size; ++i) { std::cerr << "- "; }
        node->line.debug();
        if(node->left) { std::cout << "L"; debug(node->left, size + 1); }
        if(node->right) { std::cout << "R"; debug(node->right, size + 1); }
    }
    auto debug()const { debug(m_root, 0); }
};

using ll = long long;
using std::cout;
using std::cin;
constexpr char endl = '\n';


signed main() {
    ll n, a, b, w;
    cin >> n >> a >> b >> w;
    std::vector<ll> d; d.reserve(n);
    for(int i = 0; i < n; ++i) {
        ll x; cin >> x;
        d.emplace_back(x);
    }

    constexpr ll mx = 1e18;
    std::vector<ll> dp(n + 1, mx);
    DynamicLiChaoTree<static_cast<ll>(1e6)> lct;
    auto update = [&](ll i, ll x) {
        dp[i] = x;
        auto pa = -b * i;
        auto pb = a * i + i * (i + 1) / 2 * b + dp[i];
        lct.add(pa, pb);
    };

    update(0, w);
    for(ll i = 1; i < n + 1; ++i) {
        auto ad = d[i - 1] - a * i + a + i * (i - 1) / 2 * b;
        auto min = lct.query(i);
        update(i, ad + min);
    }

    ll ans = dp[n];
    for(ll i = 0; i < n; ++i) {
        ll k = n - i;
        ans = std::min(ans, dp[i] + -a * k + k * (k + 1) / 2 * b);
    }

    cout << ans << endl;
}