"I mean what if the user enters 3072, would that code STILL work ???"

Yes.

"plz give me a working fuction, not some loose lines of code i don''t know how to use"

It''s nobody''s job around here to write your code for you. I showed more than enough to solve what you originally asked. If you are struggling understanding a for loop, the Maths and Physics Forum is probably not the best place to hang around.

Just for a point of reference of how hard this problem actually should be - I learnt that in grade 9 math - and surprisingly I still remember it! :D

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Cheers!
Brett Porter
PortaLib3D : A portable 3D game/demo libary for OpenGL