题目：
A rook is a piece used in the game of chess which is played on a board of square grids. A rook can only move vertically or horizontally from its current position and two rooks attack each other if one is on the path of the other. In the following figure, the dark squares represent the reachable locations for rook R1 from its current position. The figure also shows that the rook R1 and R2 are in attacking positions where R1 and R3 are not. R2 and R3 are also in non-attacking positions.
Now, given two numbers n and k, your job is to determine the number of ways one can put k rooks on an n x n chessboard so that no two of them are in attacking positions.
Input
Input starts with an integer T (≤ 350), denoting the number of test cases.
Each case contains two integers n (1 ≤ n ≤ 30) and k (0 ≤ k ≤ n2).
Output
For each case, print the case number and total number of ways one can put the given number of rooks on a chessboard of the given size so that no two of them are in attacking positions. You may safely assume that this number will be less than 1017.
Sample Input
8
1 1
2 1
3 1
4 1
4 2
4 3
4 4
4 5
Sample Output
Case 1: 1
Case 2: 4
Case 3: 9
Case 4: 16
Case 5: 72
Case 6: 96
Case 7: 24
Case 8: 0
就是把k个棋子，放在n*n的棋盘里面，但他们就像国际象棋中的车一样不能在同一行或同一列上，否则会被消灭
假如k大于n是肯定不可能的所以输出0
然后就是要选择 那一行 那一列有棋子
然后再哪一行和那一列匹配起来例如2 2 第二行第一行 第一列第二列都要有棋子
可以·匹配成行1列2或者行2列1两种情况