n, m = read_line.split.map(&.to_i)
a = read_line.split.map(&.to_i)
a = (0...n).map { |i| {a[i], i} }.sort
graph = (1..n).map { [] of Int32 }
m.times {
  u, v = read_line.split.map(&.to_i.pred)
  graph[u] << v
  graph[v] << u
}
k = read_line.to_i
c = read_line.split.map(&.to_i)
b = [0]*n
c.each { |i| b[i.pred] = 1 }
ans = Array(Int32).new
a.each do |(ai, i)|
  if b[i] == 0
    next
  end
  b[i] = 0
  graph[i].each do |j|
    if ai < a[j][0]
      b[j] = 1 - b[j]
    end
  end
  ans << i.succ
end
if b.sum > 0
  puts -1
else
  puts ans.size
  puts ans.join("\n")
end