Mr. S, Mr. P and Mr. Q know that there are 16 playing cards in the desk drawer: hearts A,

I suggest you use a piece of paper and write it like this:

Hearts a, q, 4

J of spades, 8, 4, 2, 7, 3

Caohua k, q, 5, 4, 6

A, block 5

Q knows the color and p knows the number of points.

P said: I didn't even know this card knew the points! =K、6、J、8、2、7、3

Q said: I know you don't know colors! Spades, grass flowers (if any, P may know). Cross out two groups of spades and flowers.

P said: Now I know the correct number of points == 1, so it can't be A, because there are two A's. Cross out hearts and diamonds.

Q said: Now I also know the number of correct colors == 1, so the color is square.

Then, it is easy to see that the answer is box 5.