#!/usr/bin/env python
# coding=utf-8

class ListNode(object):
     def __init__(self, x):
         self.val = x
         self.next = None
         

class List(object):
    def __init__(self):
        pass
    
    def make_empty(self):
        pass
        
    def is_empty(self):
        if self.next == None:
            pass
        
    def is_last(self, x):
        pass
        
    def find(self, x):
        pass
         
    def delete(self, x):
        pass
        
    def find_previous(self, x):
        pass
        
    def insert(self, x, position):
        pass

         
def main():
    pass
         
         
if __name__ == "__main__":
    main()