import java.io.*; import java.util.*; public class Main_yukicoder409_4 { private static Scanner sc; private static Printer pr; private static void solve() { int n = sc.nextInt(); long a = sc.nextInt(); long b = sc.nextInt(); long w = sc.nextInt(); int[] d = new int[n]; for (int i = 0; i < n; i++) { d[i] = sc.nextInt(); } long[] dp = new long[n + 1]; ConvexHullTrickOpt cht = new ConvexHullTrickOpt(n); for (int i = 1; i <= n; i++) { int j = i - 1; cht.add(-b * j, dp[j] + a * j + b * j * (j + 1) / 2); dp[i] = cht.query(i) + d[i - 1] - a * (i - 1) + b * i * (i - 1) / 2; } long ans = Long.MAX_VALUE; for (int i = 0; i <= n; i++) { long tmp = dp[i] - a * (n - i) + b * (n - i) * (n - i + 1) / 2; // pr.printf("%d %d %d\n", i, tmp, ans); ans = Math.min(ans, tmp); } pr.println(ans + w); } private static class ConvexHullTrickOpt { LinkedList q; // add における a が単調非増加、query における x が単調非減少である場合 // add O(n), query O(n + q) ConvexHullTrickOpt(int n) { q = new LinkedList<>(); } // ax+b を追加。a は単調非増加とする private void add(long a, long b) { Pair next = new Pair(a, b); while (q.size() >= 2) { Pair curr = q.get(q.size() - 1); Pair prev = q.get(q.size() - 2); if (check(prev, curr, next)) { break; } q.removeLast(); } q.add(next); } // f(x)の最小値。x は単調非減少とする private long query(long x) { long fx0 = fx(q.get(0), x); while (q.size() > 1) { long fx1 = fx(q.get(1), x); if (fx0 < fx1) { return fx0; } q.removeFirst(); fx0 = fx1; } return fx0; } // i 番目の直線を使った時の f(x) の値 private long fx(Pair i, long x) { return i.a * x + i.b; } // curr の直線が必要な場合 true private boolean check(Pair prev, Pair curr, Pair next) { return (next.b - curr.b) * (curr.a - prev.a) < (curr.b - prev.b) * (next.a - curr.a); } private static class Pair { long a; long b; Pair(long a, long b) { this.a = a; this.b = b; } } } // --------------------------------------------------- public static void main(String[] args) { sc = new Scanner(INPUT == null ? System.in : new ByteArrayInputStream(INPUT.getBytes())); pr = new Printer(System.out); solve(); // pr.close(); pr.flush(); // sc.close(); } static String INPUT = null; @SuppressWarnings("unused") private static class Scanner { BufferedReader br; Scanner (InputStream in) { br = new BufferedReader(new InputStreamReader(in)); } private boolean isPrintable(int ch) { return ch >= '!' && ch <= '~'; } private boolean isCRLF(int ch) { return ch == '\n' || ch == '\r' || ch == -1; } private int nextPrintable() { try { int ch; while (!isPrintable(ch = br.read())) { if (ch == -1) { throw new NoSuchElementException(); } } return ch; } catch (IOException e) { throw new NoSuchElementException(); } } String next() { try { int ch = nextPrintable(); StringBuilder sb = new StringBuilder(); do { sb.appendCodePoint(ch); } while (isPrintable(ch = br.read())); return sb.toString(); } catch (IOException e) { throw new NoSuchElementException(); } } int nextInt() { try { // parseInt from Integer.parseInt() boolean negative = false; int res = 0; int limit = -Integer.MAX_VALUE; int radix = 10; int fc = nextPrintable(); if (fc < '0') { if (fc == '-') { negative = true; limit = Integer.MIN_VALUE; } else if (fc != '+') { throw new NumberFormatException(); } fc = br.read(); } int multmin = limit / radix; int ch = fc; do { int digit = ch - '0'; if (digit < 0 || digit >= radix) { throw new NumberFormatException(); } if (res < multmin) { throw new NumberFormatException(); } res *= radix; if (res < limit + digit) { throw new NumberFormatException(); } res -= digit; } while (isPrintable(ch = br.read())); return negative ? res : -res; } catch (IOException e) { throw new NoSuchElementException(); } } long nextLong() { try { // parseLong from Long.parseLong() boolean negative = false; long res = 0; long limit = -Long.MAX_VALUE; int radix = 10; int fc = nextPrintable(); if (fc < '0') { if (fc == '-') { negative = true; limit = Long.MIN_VALUE; } else if (fc != '+') { throw new NumberFormatException(); } fc = br.read(); } long multmin = limit / radix; int ch = fc; do { int digit = ch - '0'; if (digit < 0 || digit >= radix) { throw new NumberFormatException(); } if (res < multmin) { throw new NumberFormatException(); } res *= radix; if (res < limit + digit) { throw new NumberFormatException(); } res -= digit; } while (isPrintable(ch = br.read())); return negative ? res : -res; } catch (IOException e) { throw new NoSuchElementException(); } } float nextFloat() { return Float.parseFloat(next()); } double nextDouble() { return Double.parseDouble(next()); } String nextLine() { try { int ch; while (isCRLF(ch = br.read())) { if (ch == -1) { throw new NoSuchElementException(); } } StringBuilder sb = new StringBuilder(); do { sb.appendCodePoint(ch); } while (!isCRLF(ch = br.read())); return sb.toString(); } catch (IOException e) { throw new NoSuchElementException(); } } void close() { try { br.close(); } catch (IOException e) { // throw new NoSuchElementException(); } } } private static class Printer extends PrintWriter { Printer(OutputStream out) { super(out); } } }