You are diagnosed with a deadly disease and are prescribed 2 different sets of pills. You must take only one of each pill every day to survive. If you take two of the same pill, you grow a tail and die a painful death.
But silly you! With only two days left on your prescription, you accidentally drop your four remaining pills and they get mixed up. I don't know where you're buying your pills. They're probably from somewhere in Eastern Europe. You have no way of telling the pills apart.
How do you make sure you take the correct medication?