题目描述
Alice and Bob were playing a game yet again but this time, Bob already lost the game. Now he wants to take revenge.
Bob saw a jigsaw puzzle which was solved by Alice and decided to jumble the puzzle pieces again. There are N puzzle pieces in a line numbered from 1 to N in increasing order and he has K minutes before Alice catches him.
Bob can swap any two pieces of the puzzle. Each swap takes 1 minute, and so Bob can make at most K swaps.
Let A_{i} denote the piece in the i-th position after Bob finishes making his swaps.
Alice's angriness is defined to be the number of pairs (i, j) such that 1 ≤ i < j ≤ N and A_{i} > A_{j}.
Bob would like to make Alice as angry as possible, so he asks for your help: if he performs his swaps optimally, what is the maximum angriness he can achieve?
------ Input Format ------
- The first line of input contains an integer T, denoting the number of test cases.
- The first and only line of each test case contains two space-separated integers N and K: the number of pieces and the number of swaps Bob can make.
------ Output Format ------
- For each test case, output on a new line a single integer: Alice's maximum possible angriness.
------ Constraints ------
$1 ≤ T ≤ 10^{5}$
$1 ≤ N ≤ 10^{9}$
$1 ≤ K ≤ 10^{9}$
----- Sample Input 1 ------
4
7 3
1 4
8 2
5 3
----- Sample Output 1 ------
21
0
22
10
----- explanation 1 ------
Test case $1$: $N = 7$, so the pieces are initially arranged as $[1, 2, 3, 4, 5, 6, 7]$. Bob can make $K = 3$ swaps. One optimal way of swapping is as follows:
- First, swap $2$ and $6$. Now the pieces are $[1, 6, 3, 4, 5, 2, 7]$
- Next, swap $1$ and $7$. Now the pieces are $[7, 6, 3, 4, 5, 2, 1]$
- Finally, swap $3$ and $5$. Now the pieces are $[7, 6, 5, 4, 3, 2, 1]$
The angriness of this sequence is $21$, which is the maximum possible.
Test case $2$: $N = 1$, so no swaps can be made. The answer is always $0$.
输入格式
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输出格式
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