package contest; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; public class N409_3 { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(); long a = ni(), b = ni(), w = ni(); int[] d = Arrays.copyOf(na(n), n+1); long[] dp = new long[n+2]; dp[0] = w; // dp+b(x-t)(x-t-1)/2-a(x-t) // b/2*x^2+x((-bt-bt+b)/2-a)+dp+bt(t+1)/2+at if(b == 0){ out.println(w-(long)a*n); return; } int[] q = new int[n+2]; long[] qw = new long[n+2]; int ind = 0; int qp = 0; for(int i = 1;i <= n+1;i++){ int x = i-1; long B = -b*x; long C = dp[x] + b*x*(x+1)/2+a*x; long lwhen = Long.MIN_VALUE; while(qp > 0){ int lx = q[qp-1]; long LB = -b*lx; long LC = dp[lx] + b*lx*(lx+1)/2+a*lx; // B*x+C <= LB*x+LC long when = (C-LC+(LB-B-1))/(LB-B); if(qw[qp-1] >= when){ qp--; }else{ lwhen = when; break; } } q[qp] = x; qw[qp] = lwhen; qp++; ind = Math.min(ind, qp-1); while(ind+1 < qp && qw[ind+1] <= i){ ind++; } x = q[ind]; long val = dp[x] + b*(i-x)*(i-x-1)/2 - a*(i-x-1); dp[i] = val + d[i-1]; } out.println(dp[n+1]); } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new N409_3().run(); } private byte[] inbuf = new byte[1024]; private int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }