23
a
3
-6
8
-7
b
9
7
-5
-9
C
5
11
-7
-2
a + b + c
a-b+c
a+b-c
a-b-c


23 A 3 6 8 7 B 9 7 5 9 C 5 11 7 2 A B C Abc Abc Abc class=