teacher has 2 red caps and 3 white caps. He asks his smartest three students A,
B and C to stand in so that C can see A and B, B can see A, and A can stand
however she wants. Now, the teacher asks them to close their eyes and wear one
cap one their head each, then he hides all other caps. After they open their
eyes, only A can tell the color of her cap, as everyone announces whether or
not they can determine their hat color. What color is As hat?