4 
1 2
2
3 4
3
5
?
4 8
2
1
3
7
44 16
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
23
1