 Server Time: Sun Oct 25, 2020 10:56 am
 Welcome ( logout ) N - Positive Negative Sign PDF (English) Ranklist
 Time Limit: 2 second(s) Memory Limit: 32 MB

Given two integers: n and m and n is divisible by 2m, you have to write down the first n natural numbers in the following form. At first take first m integers and make their sign negative, then take next m integers and make their sign positive, the next m integers should have negative signs and continue this procedure until all the n integers have been assigned a sign. For example, let n be 12 and m be 3. Then we have

-1 -2 -3 +4 +5 +6 -7 -8 -9 +10 +11 +12

If n = 4 and m = 1, then we have

-1 +2 -3 +4

Now your task is to find the summation of the numbers considering their signs.

# Input

Input starts with an integer T (≤ 10000), denoting the number of test cases.

Each case starts with a line containing two integers: n and m (2 ≤ n ≤ 109, 1 ≤ m). And you can assume that n is divisible by 2*m.

# Output

For each case, print the case number and the summation.

# Output for Sample Input

2

12 3

4 1

Case 1: 18

Case 2: 2

Problem Setter: Jane Alam Jan
 Developed and Maintained by JANE ALAM JAN Copyright © 2012 LightOJ, Jane Alam Jan