19 - ( -20 ) =
7 - ( + 19 ) - ( 20 ) =
- ( 8 ) - ( - 13 ) - ( + 21 ) =
- ( + 7 ) - ( - 3 ) - ( - 2 ) =
8 - ( -12 ) - ( + 19 ) =
15 - ( -13 ) =
- ( 4 ) - ( - 8 ) =
( -3 ) - ( +6)=
- ( 5 ) - ( - 3 ) - ( + 6 ) - ( - 7 )=
- ( 6 ) - ( +12 ) =
-1
-32
1
28
-9
-2
-18
-16
39
4