#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <set>
#include <map>
#include <queue>
#include <tuple>
#include <unordered_set>
#include <unordered_map>
#include <functional>
#include <cassert>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
#define repeat_from(i,m,n) for (int i = (m); (i) < (n); ++(i))
#define repeat_reverse(i,n) for (int i = (n)-1; (i) >= 0; --(i))
#define repeat_from_reverse(i,m,n) for (int i = (n)-1; (i) >= (m); --(i))
#define whole(f,x,...) ([&](decltype((x)) y) { return (f)(begin(y), end(y), ## __VA_ARGS__); })(x)
typedef long long ll;
using namespace std;
template <class T> void setmax(T & a, T const & b) { if (a < b) a = b; }
template <class T> void setmin(T & a, T const & b) { if (b < a) a = b; }
const ll inf = ll(1e18)+9;
int main() {
    // input
    int n, a, b, w; cin >> n >> a >> b >> w;
    vector<int> d(n); repeat (i,n) cin >> d[i];
    // compute
    n += 1;
    d.push_back(0);
    vector<ll> dp(n+1);
    vector<ll> min_dp(n+1);
    dp[0] = w;
    min_dp[0] = w;
    repeat (i,n) {
        ll acc = inf;
        repeat_reverse (j,i+1) {
            int l = i-j+1;
            setmin(acc, dp[j] - a*l + b*l*(l+1)/2);
            // if (a < b * (i-j+1)/2 and min_dp[j] - a * (i-j) + b * (i-j)*(i-j+1)/2 > acc) break;
        }
        dp[i+1] = acc + d[i];
        min_dp[i+1] = min(min_dp[i], dp[i+1]);
    }
    // output
    cout << dp[n] << endl;
    return 0;
}