program main
  implicit none
  integer*8::N,M,K,i,j,l,src,dest
  integer*8,allocatable::road(:,:)
  integer*8,allocatable::list(:,:,:)
  integer*8,allocatable::listnum(:)
  integer*8,allocatable::keiro(:)
  integer*8,allocatable::han1(:),han2(:)
  integer*8::ryoukin, num, tmp

  read *,N,M,K
  allocate(road(3,M))
  allocate(list(2,N,M))
  allocate(listnum(N))
  allocate(keiro(K))
  allocate(han1(N))
  allocate(han2(N))
  read *, road
  read *, keiro

  list = 0
  listnum = 0

  do i=1,M
     src  =    road(1,i)
     dest =    road(2,i)
     ryoukin = road(3,i)

     listnum(src)  = listnum(src)  + 1
     listnum(dest) = listnum(dest) + 1

     list(1, src,  listnum(src))  = dest
     list(1, dest, listnum(dest)) = src
     list(2, src,  listnum(src))  = ryoukin
     list(2, dest, listnum(dest)) = ryoukin
  end do

  han1 = 1
  han2 = 0
  do i=1, K
     ryoukin = keiro(i)
     do j=1, N
        if(han1(j).eq.1) then
           tmp = listnum(j)
           do l=1, tmp
              if(list(2,j,l).eq.ryoukin) then
                 han2(list(1,j,l)) = 1
              end if
           end do
        end if
     end do
     han1 = han2
     han2 = 0
  end do

  num = SUM(han1)
  print '(i0)', num
  do i=1,N
     if(han1(i).eq.1) then
        num = num - 1
        if(num.ne.0) then
           write(6,'(i0,a)',advance='no') i, " "
        else
           write(6,'(i0)') i
        end if
     end if
  end do
end program main