class BinaryTree:
    def __init__(self):       self.tree = EmptyNode()
    def __repr__(self):       return `self.tree`
    def lookup(self, value):  return self.tree.lookup(value)
    def insert(self, value):  self.tree = self.tree.insert(value)

class EmptyNode:
    def __repr__(self):
        return '*'
    def lookup(self, value):                      # fail at the bottom
        return 0
    def insert(self, value):
        return BinaryNode(self, value, self)      # add new node at bottom

class BinaryNode:
    def __init__(self, left, value, right):
        self.data, self.left, self.right  =  value, left, right
    def lookup(self, value):
        if self.data == value:
            return 1
        elif self.data > value:
            return self.left.lookup(value)               # look in left
        else:
            return self.right.lookup(value)              # look in right
    def insert(self, value):
        if self.data > value:
            self.left = self.left.insert(value)          # grow in left
        elif self.data < value:
            self.right = self.right.insert(value)        # grow in right
        return self
    def __repr__(self):
        return '( %s, %s, %s )' % (`self.left`, `self.data`, `self.right`)