A guessing game between two persons, say, A and B, is of interest. First, without letting the other knows, A and B each put a certain amount of money into a box. The goal is to guess the total money in the box, and the one with into a box. the correct guess wins the game and takes away all the money. A guesses first, and then B. We are interested in the advantage of B over A, and simulation are performed to compare with the result derived.