If you do not know what "enumeration" means- look it up! If you do, then you should understand that the problem is simply subtracting integers. Surey, you know how to do that!
well actually i was trying to solve that but i when i attempt all answers are 0.
x-y = 1- 1 = 0, or 2-2 = 0 or 3 -3 = 0 ... there must something wrong with the problem if these are not the answer.
P.S... HallsOfIvy you are not impressive though. your answers are making things complicated ... you are not a help! you are only pretending