#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
#define repeat_reverse(i,n) for (int i = (n)-1; (i) >= 0; --(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 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];
    if (b == 0) {
        // output
        cout << w - a*(ll)n << endl;
    } else {
        // dp
        n += 1;
        d.push_back(0);
        int limit = 2 * sqrt((*whole(max_element, d) + a) / b) + 3;
        vector<ll> dp(n+1);
        dp[0] = w;
        repeat (i,n) {
            ll acc = inf;
            repeat_reverse (j,i+1) {
                setmin(acc, dp[j] - a *(ll) ll(i-j) + b *(ll) (i-j)*(i-j+1)/2);
                if (i-j > limit) break;
            }
            dp[i+1] = acc + d[i];
        }
        // output
        cout << dp[n] << endl;
    }
    return 0;
}