class node:
   def __init__(self,val):
    self.val=root
    self.right=right
    self.left=left
     
    def inorder():
        self.left=left
        self.root=val
        self.right=right
        
    def preorder():
        self.root=val
        self.left=left
        self.right=right
        
    def postorder():
        self.left=left
        self.right=right
        self.root=val
        
     if(n<0):
         print("Invalid input")
         
    n=node()
    n.inorder()