"It's your birthday and I want to give you a present, but since unwrapping a present is half the fun I've put your present inside of a little box which is inside of a bigger box - which is inside of an even bigger box! The problem is I don't even remember how many boxes are inside of each other; so you'll just have to open each box and check if the present is there. Once you find your present you can go outside and show it to your friends, but until you find it you'll have to keep opening the boxes. Here's your boxed present - have fun!"