SUM things are the
PRODUCT of twisted minds!

Two people, named S and P, are talking about two numbers x and y. 
(note: x and y are both integers greater than or equal to 2). S 
knows their sum (x+y), while P knows their product (xy); however, 
initially NEITHER knows x and y.

S: Hey P! I don't know what the numbers are.
P: I'm not surprised. I KNEW you didn't know. However, I too don't 
   know.
S: You don't? Really! Then I know what the numbers are!

What are the two numbers? (communicated by Kathryn Sievers)