Computer Programming Contest Preparation

    1 20
    2 FF + F
    3 ABC + CDE
    4 AA + 991
    5 F0C + A
    6 FFF - FFF
    7 AA + DDD
    8 FFF - CCD
    9 DDA - C9C
   10 E0A - ABB
   11 C - 9
   12 A + B
   13 FFF - 123
   14 36 + 2
   15 0 + 0
   16 3 - 0
   17 23 - 1
   18 A46 - 1A
   19 F - 1
   20 14 - 13
   21 988 - FA
   22