As we all know, Harry Porter learns magic at Hogwarts School. However, learning magical knowledge alone is insufficient to become a great magician. Sometimes, Harry also has to gain knowledge from other certain subjects, such as language, mathematics, English, and even algorithm.
Today, Harry's physical teacher set him a difficult problem: if a small ball moving with a speed $V_0$ made a completely elastic collision with a car moving towards the same direction with a speed $V (V
Input
They are several test cases, you should process to the end of file.
There are two integers $V$ and $V_0$ for each test case. All the integers are 32-bit signed non-negative integers.
Output
For each test case, just output one line that contains an integer indicate the speed of the small ball after the collision.
