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 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 ≤ 10^{9}, 1 ≤ m). And you can assume that n is divisible by 2*m.
For each case, print the case number and the summation.
Sample Input |
Output for Sample Input |
2 12 3 4 1 |
Case 1: 18 Case 2: 2 |
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