#include <bits/stdc++.h>
using namespace std;

template<class Numeric> struct ConvexHullTrick {
  struct Line { // f: y=ax+b
    Numeric a; Numeric b;
    Line(Numeric _a, Numeric _b) : a(_a), b(_b) {}
    bool operator< (Line &l) {
      if (a != l.a) return a < l.a;
      else return b < l.b;
    }
  };

  private:
    vector<Line> lines;
    bool isMinimumQuery;
    bool isMonotonicQuery;
    bool compare(Numeric a, Numeric b) {
      if (isMinimumQuery) return b <= a;
      else return a <= b;
    }

  public:
    // constructor
    ConvexHullTrick(bool monotonic, bool minimum = true) :
      isMinimumQuery(minimum), isMonotonicQuery(monotonic) {}
    // check the necessity of line2
    bool check(Line l1, Line l2, Line l3) {
      if (l1 < l3) swap(l3, l1);
      return compare((l3.b-l2.b)*(l2.a-l1.a), (l2.b-l1.b)*(l3.a-l2.a));
    }
    // add the line: y=ax+b
    void add(Numeric a, Numeric b) {
      Line line(a, b);
      int size = (int) lines.size();
      while (size >= 2 && check(lines[size-2], lines[size-1], line)){
        lines.pop_back(); --size;
      }
      lines.emplace_back(line);
    }
    // get the value of line(x)
    Numeric f(Line line, Numeric x) {
      return line.a * x + line.b;
    }
    // solve
    Numeric solve(Numeric x) {
      if (isMonotonicQuery) {
        static int head = 0;
        while (lines.size() - head >= 2 && compare(f(lines[head], x), f(lines[head+1], x))) ++head;
        return f(lines[head], x);
      }
      else {
        int low = -1; int high = lines.size()-1;
        while (high - low > 1) {
          int mid = (high+low)/2;
          if (compare(f(lines[mid], x), f(lines[mid+1], x))) low = mid;
          else high = mid;
        }
        return f(lines[high], x);
      }
    }

};

int main(){
  long long n, a, b, w; cin >> n >> a >> b >> w;
  vector<long long> d(n);
  for (long long i = 0; i < n; i++) {
    cin >> d[i];
  }
  vector<long long> dp(n+1, 0);
  ConvexHullTrick<long long> convexhulltrick(true);
  for (long long i = 0; i < n; i++) {
    convexhulltrick.add(-i*b, dp[i]+i*a+(i+1)*i*b/2);
    dp[i+1] = convexhulltrick.solve(i+1) - a*i + (i+1)*i*b/2 + d[i];
  }
  long long ans = 1e18;
  for (long long i = 0; i <= n; i++) {
    ans = min(ans, w+dp[i]-(n-i)*a+(n-i)*(n-i+1)*b/2);
  }
  cout << ans << endl;
  return 0;
}