program	main
  implicit none
  integer(8)::n,a,b,i
  integer(8),allocatable::x(:)
  read*,n,a,b
  allocate(x(n))
  read*,x
  forall(i=1:n-1)x(i)=(x(i+1)-x(i))*a
  where(x>b)x=b
  x(n)=0
  print'(i0)',sum(x)
end program main