2
3
4
() 18 5
6
7
() 8
1 2 3 () 4 1 9
10
1 11
12
13
14
8 1 74 11 15
16
1 17
18
19
20
21
18 A 18 B C A+B-C 0 0 0 0 18 A 18 B C A+B-C 0 0 0 0 22