class List:
    def __init__(self):
   	 self.item = None
   	 self.rest = None

    def append(self, item):
   	 if self.rest is None:
   		 self.rest = Link(item)
   	 else:
   		 self.rest.append(item)
    def __len__(self):
   	 if self.rest is None:
   		 return 0
   	 else:
   		 return 1 + len(self.rest)

    def __repr__(self):
   	 if self.rest is None:
   		 return "[]"
   	 else:
   		 return "[" + repr(self.rest) + "]"

class Link:
    def __init__(self, item):
   	 self.item = item
   	 self.links = None

    def append(self, item):
   	 if self.links is None:
   		 self.links = Link(item)
   	 else:
   		 self.links.append(item)

    def __len__(self):
   	 if self.links is None:
   		 return 0
   	 else:
   		 return 1 + len(self.links)
    
    def __repr__(self):
   	 if self.links is None:
   		 return str(self.item)
   	 else:
   		 return str(self.item) + '; ' + repr(self.links)