(         )

  
 ︾       
       
  ︽ ︿     ﹀   

 
         
           
        
         
         
         
           

 
          
         
           
           
         
            

        
          
         
            
           
          
           
        
           
           

       
         
       ︽     ︾
          
           
           
         
       
    18  30       
        

         
    ︽     ︾   
         
        
         
 ︾      16    
        ︽   