3
 20,18,17,16,13,21,15,14,10,9,8,7,6,12
3.1
 7
3.2
 8
3.2.1
 9
3.2.2
 10
3.2.3
 13
3.2.4
 14
3.2.5
 15
3.3
 16
3.3.1
 17
3.3.2
 18
3.3.3
 20
3.4
 21