  
  ①         
          
  ②      
③         
④         
       
         
         
              
             
             
              

        
           
           
        
         
       
            
            
             
           
       
            
           
             
             
        
             
               
         
              

         
            
         
         
          
         
         
          
            
           
            
            
           
         
           
         
             
            
           
            

           
          
        
         
         
       
         
         
              
             
             
              




 
①②③④        