[Wf2011]Chips Challenge

时间限制:10s      空间限制:128MB

题目描述

有一个芯片,芯片上有N*N(1≤N≤40)个插槽,可以在里面装零件。

有些插槽不能装零件,有些插槽必须装零件,剩下的插槽随意。

要求装好之后满足如下两条要求:

1、第 i 行和第 i 列的零件数目必须一样多(1≤i≤N)。

2、第 i 行的零件数目不能超过总的零件数目的 A/B(1≤i≤N,0≤A≤B≤1000,B≠0)。

求最多可以另外放多少个零件(就是除掉必须放的)。如果无解输出impossible。


输入格式

The input consists of several test cases. Each case starts with a line containing three integers: The size of the chip N (1<=N<=40), and A and B (1<=A<=1000, 0<=A<=B) as described above. Each of the following N lines contains N characters describing the slots, one of `.', `/' or `C', as described above.

The last test case is followed by a line containing three zeros.


输出格式

For each test case, display a single line beginning with the case number. If there is a solution, display the maximum number of widgets that can be added to the chip. Display ``impossible" if there is no solution.

Follow the format of the sample output.


样例输入

2 1 1
/.
//
2 50 100
/.
C/
2 100 100
./
C.
5 3 10
CC/..
././/
..C.C
/.C..
/./C/
5 2 10
CC/..
././/
..C.C
/.C..
/./C/
0 0 0


样例输出

Case 1: 0
Case 2: 1         
Case 3: impossible
Case 4: 7         
Case 5: impossible


提示

没有写明提示


题目来源

没有写明来源