n, a, b, w = map(int, input().split())
D = [0]+list(map(int, input().split()))+[0]

if b==0:
  print(w-n*a)
  exit()
dp = [1<<60]*-~n
dp[0] = w
calcx = lambda j: dp[j]+(j+1)*a+b*(j**2+j)//2
calc = lambda i, j: (calcx(i)-calcx(j))/(b*(i-j))
calcmin = lambda i, j: calcx(j)-b*i*j
calcall = lambda i, j: D[i]-i*a+b*(i**2-i)//2+calcmin(i, j)

from collections import deque
stack = deque([0])
ans = 0
num = 0
length = 1
for i in range(1, n+2):
  d = D[i]
  while length>=2 and calcmin(i, stack[0])>=calcmin(i, stack[1]):
    stack.popleft()
    length -= 1
  if i==n+1:
    # print(dp)
    print(dp[stack[0]]+(n-stack[0])*(n-stack[0]+1)//2*b-a*(n-stack[0]))
    exit()
  dp[i] = calcall(i, stack[0])
  while length>=2 and calc(stack[-1], stack[-2])>=calc(stack[-1], i):
    stack.pop()
    length -= 1
  stack.append(i)
  length += 1
  # print(stack)