n, a, b, w = map(int, input().split())
D = list(map(int, input().split()))

from collections import deque
stack = deque([1<<60])
ans = 0
num = 0
for d in D:
  while stack and stack[-1]>d:
    stack.pop()
  stack.append(d)
  if stack and b*(num+1)-a>stack[-1]:
    ans += stack.popleft()
    num = 0
  else:
    num += 1
    ans += b*num-a

print(ans+w)