id: 20 media ( 8, (6, 0, 0, 2)) (( 0.7, 0.8 ), ( 2.6, 0.8 ))
 +4        |               +2 
         |                
         |      2016 12      2018 17 11  
    +    +    +    +    + 
         |                
         |               
         |                
         |                
    +    +    +    +    + 
         2013      2015         
         |                
         |                
         |                
    +    +    +    +    + 
         |                
         |                
  2014      |                
         |                
    +    +    +    +    + 
         |                
         |                
         |                
         |                
 0---+----+----+----+----+-1