def cross(*args):
  """ compute cross-product of args """
  ans = []
  for arg in args[0]:
    for arg2 in args[1]:
      ans.append(arg+arg2)
  return ans
  #alternatively:
  #ans = [[]]
  #for arg in args:
    #ans = [x+y for x in ans for y in arg]
  
  #return ans