How to calculate if there is a coin standing upright when telling fortune?

I've met this situation several times, so I don't need to change my mind again. This is an external response. If I stand up straight, I will see one side. If it is perpendicular to my eyes (which is very unlikely), the method of changing friends on the third floor is not bad. Or if the coin falls to the ground, you don't have to shake it again. Just find the coin and look at the front and back. It will not affect divination at all.