interesting math riddle

[furyshade]

my friend showed me this today, he doesn't know the answer and it has been bugging me, anyone wanna give a shot at it? please dont just look up answer, and if you know it don't post it. oh and my friend said it is a math riddle, not some trick like "turn on the light".

There are 50 coins, 18 heads up, 32 tails up in a dark room. You want to make two piles that have an equal number of heads. (You don't care what size these piles are, and the piles don't necessarily have to be the same size as each other. So, for instance, if you had a way to verify that two coils were tails, you could put them in two separate piles of 1 coin each, and you'd be done.) You cannot feel the coins or anything like that. The only thing you can do is move them around and flip them.