I was trying to solve an exercise while studying basic probabilities and while solving the exercise, I thought of this problem which I thought was fun, so I decided to share it with my fellow noobs :)

Please if you're anything above a newbie, (in Ercole Visconti's voice) This problem is not for you (no offence) :)

Problem Statement

You have n tiles numbered from 1 through to n. You are also given an integer K. The task it to count all pairs of integers (a,b) from the n tiles whose difference is K. that means (a — b) = K

Input The one and only line of the input contains two positive integer n and K. Output Print the number of such pairs (a, b) whose difference is K, thank you.

Sample input 100 11 Sample output 89