class Yukicoder
  def initialize
    n, m, k = gets.chomp.split(' ').map(&:to_i)
    paths = Hash.new{|h,k| h[k] = Hash.new{|h,k| h[k] = []}}

    m.times do
      a, b, c = gets.chomp.split(' ').map(&:to_i)
      paths[a][c] << b
      paths[b][c] << a
    end

    d = gets.chomp.split(' ').map(&:to_i)

    current = [*(1..n)]

    d.each do |cost|
      temp = []

      current.each do |i|
        temp |= paths[i][cost]
      end

      current = temp.dup
    end

    puts current.size
    puts current.sort.join(' ')
  end
end

Yukicoder.new