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
		long a = nl();// the effet of fasting
		long b = nl();// the effect of stress
		long w = nl();// current weight
		long[] d = new long[n];
		for (int i = 0; i < n; i++) {
			d[i] = nl();
		}
		/*
		 * 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];
		long[] F = new long[n + 1];
		F[0] = w;

		int s = 0;
		int t = 1;
		for (int i = 1; i <= n; i++) {
			while (s + 1 < t && f(deq[s], i, d, b, a, F) >= f(deq[s + 1], i, d, b, a, F))
				s++;
			F[i] = f(deq[s], i, d, b, a, F) + (long)d[i - 1] - (long)(i - 1) *(long) a + ((long)i * (long)i - (long)i) / 2 * (long)b;
			while (s + 1 < t && check(deq[t - 2], deq[t - 1], i, b, F, a))
				t--;
			deq[t++] = i;
		}
		long ans = 1L << 60;
		for (int i = 0; i <= n; i++) {
			long D = n - i;
			ans = Math.min(ans, F[i] + (long) b * ((long) D + 1L) * (long) D / 2 - (long) a * (long) 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, long b, long[] F, long a) {
		long a1 = -(long) k1 * (long) b;
		long a2 = -(long) k2 * (long) b;
		long a3 = -(long) k3 * (long) b;
		long b1 = F[k1] + (long) k1 * (long) a + ((long) k1 * (long) k1 + (long) k1) / 2 * (long) b;
		long b2 = F[k2] + (long) k2 * (long) a + ((long) k2 * (long) k2 + (long) k2) / 2 * (long) b;
		long b3 = F[k3] + (long) k3 * (long) a + ((long) k3 * (long) k3 + (long) k3) / 2 * (long) b;
		return ( a2 - a1) * ( b3 - b1) >= (b1 - b2) * ( a1 -  a3);

	}

	static long f(int j, long x, long[] d, long b, long a, long[] F) {
		return -(long) j * (long) b * (long) x + F[j] + (long) j * (long) a
				+ ((long) j * (long) j + (long) j) / 2 * (long) b;
	}

	static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}
}