activation

hi.! im new here.. and sorry for asking a help..but i really need it..

umm.. lets go to the point..
i just bought a crysis 2 game ..
i installed it..
and it's installed ..

now i want to play,really want to play it.. so i click the icon.. but i got the "product activation" code message..
i realize i dont have it..
i dont know what to do..

does anyone here can help me or know the "product activation" code..?
please help me ..
i already checked my version.. it's 1.8 , hope that information can be useful..

If you really did buy this game you got cd key on the case if not there are cracks

yah, i bought it..
but maybe it's a pirated cd(crack) .. because it's cheap.. about 2 dollars.. uhuhuhh..

well, do you know how can i play it..? ignore/remove the product activation code , if its a crack..?