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

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

  dp(0) = W + D(1)
  dp(1) = W - A + B*1
  if(B.eq.0) then
     print '(i0)',W-N*A
     return
  else
     uplimit = A/B
  end if

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

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

end program