CF924D Contact ATC

Arkady the air traffic controller is now working with $ n $ planes in the air. All planes move along a straight coordinate axis with Arkady's station being at point $ 0 $ on it. The $ i $ -th plane, small enough to be represented by a point, currently has a coordinate of $ x_{i} $ and is moving with speed $ v_{i} $ . It's guaranteed that $ x_{i}·v_{i}

The first line contains two integers $ n $ and $ w $ ( $ 1

Output a single integer — the number of unordered pairs of planes that can contact Arkady at the same moment.

In the first example, the following $ 3 $ pairs of planes satisfy the requirements: - $ (2,5) $ passes the station at time $ 3/4 $ with $ v_{wind}=1 $ ; - $ (3,4) $ passes the station at time $ 2/5 $ with $ v_{wind}=1/2 $ ; - $ (3,5) $ passes the station at time $ 4/7 $ with $ v_{wind}=-1/4 $ . In the second example, each of the $ 3 $ planes with negative coordinates can form a valid pair with each of the other $ 3 $ , totaling $ 9 $ pairs.