def insert(self, val):
        if self.val:
            if val < self.val:
                if self.left is None:
                    self.left = Node(val)
                else:
                    self.left.insert(val)
            elif val > self.val:
                if self.right is None:
                    self.right = Node(val)
                else:
                    self.right.insert(val)
        else:
            self.val = val