program main
  implicit none
  integer*8::DA
  integer*8,allocatable::a(:)
  integer*8::b0,b1,b2
  integer::i
  read *,DA
  allocate(a(0:DA))
  read *,a(0:DA)

  b2 = SUM(a(2:DA:2))
  b1 = SUM(a(1:DA:2))
  b0 = a(0)

  if(b2.ne.0) then
     print '(i0)', 2
     print '(i0,1x,i0,1x,i0)', b0,b1,b2
  else if(b1.ne.0) then
     print '(i0)', 1
     print '(i0,1x,i0)', b0,b1
  else
     print '(i0)', 0
     print '(i0)', b0
  end if
end program main