program main
  implicit none
  integer*8::N,A,B,W,i,j
  integer*8,allocatable::D(:)
  integer*8,allocatable::dp(:),pdp(:)

  read *, N,A,B,W
  allocate(D(N))
  allocate(dp(0:N))
  allocate(pdp(0:N))
  read *, D

  dp(0) = W + D(1)
  dp(1) = W - A + B*1

  do i=2,N
     pdp(0:i-1) = dp(0:i-1)
     dp = MINVAL(pdp(0:i-1)) + D(i)
     do j=1,i
        dp(j) = pdp(j-1) - A + B*j
     end do
  end do

  print '(i0)', MINVAL(dp(0:N))

end program