Competitions
PP1 and Competitive Programming
Easy problem for Dino
The math teacher asks Dino a very simple question: Given two different integers a and b. Find such integer k that a  k = b  k. Warning: x means absolute value.
Input
Two integers a and b (10^{9}
≤ a, b ≤ 10^{9}
, a ≠ b).
Output
If the value of k doesn't exist, print  , otherwise print k.
Input example #1
10 5
Output example #1

Input example #2
6 2
Output example #2
4