A woman wants to enter an exclusive club, but she doesn’t know the password. A man walks to the door and the doorman says 12, the man says 6 and is let in. Another man walks up and the doorman says 6, the man says 3 and is let in. Thinking she’s figured it out, she walks up to the door and the doorman says 10, she says 5, and she isn’t let in. What should she have said?