package No400番台; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.Scanner; public class Main { static InputStream is; static PrintWriter out; static String INPUT = ""; public static void main(String[] args) throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); solver(); out.flush(); } static long nl() { try { long num = 0; boolean minus = false; while ((num = is.read()) != -1 && !((num >= '0' && num <= '9') || num == '-')) ; if (num == '-') { num = 0; minus = true; } else { num -= '0'; } while (true) { int b = is.read(); if (b >= '0' && b <= '9') { num = num * 10 + (b - '0'); } else { return minus ? -num : num; } } } catch (IOException e) { } return -1; } static char nc() { try { int b = skip(); if (b == -1) return 0; return (char) b; } catch (IOException e) { } return 0; } static double nd() { try { return Double.parseDouble(ns()); } catch (Exception e) { } return 0; } static String ns() { try { int b = skip(); StringBuilder sb = new StringBuilder(); if (b == -1) return ""; sb.append((char) b); while (true) { b = is.read(); if (b == -1) return sb.toString(); if (b <= ' ') return sb.toString(); sb.append((char) b); } } catch (IOException e) { } return ""; } public static char[] ns(int n) { char[] buf = new char[n]; try { int b = skip(), p = 0; if (b == -1) return null; buf[p++] = (char) b; while (p < n) { b = is.read(); if (b == -1 || b <= ' ') break; buf[p++] = (char) b; } return Arrays.copyOf(buf, p); } catch (IOException e) { } return null; } public static byte[] nse(int n) { byte[] buf = new byte[n]; try { int b = skip(); if (b == -1) return null; is.read(buf); return buf; } catch (IOException e) { } return null; } static int skip() throws IOException { int b; while ((b = is.read()) != -1 && !(b >= 33 && b <= 126)) ; return b; } static boolean eof() { try { is.mark(1000); int b = skip(); is.reset(); return b == -1; } catch (IOException e) { return true; } } static int ni() { try { int num = 0; boolean minus = false; while ((num = is.read()) != -1 && !((num >= '0' && num <= '9') || num == '-')) ; if (num == '-') { num = 0; minus = true; } else { num -= '0'; } while (true) { int b = is.read(); if (b >= '0' && b <= '9') { num = num * 10 + (b - '0'); } else { return minus ? -num : num; } } } catch (IOException e) { } return -1; } static void solver() { Scanner sc = new Scanner(System.in); int n = ni();// the duration int a = ni();// the effet of fasting int b = ni();// the effect of stress int w = ni();// current weight int[] d = new int[n]; for (int i = 0; i < n; i++) { d[i] = ni(); } /* * F[0]=W F[k]=D[k]+min(F[i]+(k-i-1)*(k-i)/2*B-(k-i-1)*A) (0<=i<=k-1) * * answer:min(F[i]-(n-i)*A+1/2*(n-i)(n-i+1)*B) (0<=i<=n) * * F[k]=D[k]-(k-1)*A+(k-1)*k/2*B+min(F[i]+-ikB+i*(i+1)/2*B+iA) */ int[] deq = new int[n + 3]; int[] F = new int[n + 1]; F[0] = w; int s = 0; int t = 1; for (int i = 1; i <= n; i++) { while(s+1=f(deq[s+1],i,d,b,a,F))s++; F[i] = f(deq[s],i, d, b, a, F) + d[i - 1] - (i - 1) * a + (i * i - i) / 2 * b; while (s + 1 < t && check(deq[t - 2], deq[t - 1], i, b, F, a)) t--; deq[t++] = i; } long ans=1<<60; for(int i=0;i<=n;i++){ long D=n-i; ans=Math.min(ans, F[i]+b*(D+1)*D/2-a*D); } System.out.println(ans); } static class Pair { long a, b; Pair(long a, long b) { this.a = a; this.b = b; } } static boolean check(int k1, int k2, int k3, int b, int[] F, int a) { int a1 = -k1 * b; int a2 = -k2 * b; int a3 = -k3 * b; int b1 = F[k1] + k1 * a + (k1 * k1 + k1) / 2 * b; int b2 = F[k2] + k2 * a + (k2 * k2 + k2) / 2 * b; int b3 = F[k3] + k3 * a + (k3 * k3 + k3) / 2 * b; return (a2 - a1) * (b3 - b1) >= (b1 - b2) * (a1 - a3); } static int f(int j, int x, int[] d, int b, int a, int[] F) { return -j * b * x + F[j] + j * a + (j * j + j) / 2 * b; } static void tr(Object...o){System.out.println(Arrays.deepToString(o));} }