题目描述

The cows have a new laser-based system so they can have casual conversations while out in the pasture which is modeled as a W x H grid of points (1 <= W <= 100; 1 <= H <= 100).
The system requires a sort of line-of-sight connectivity in order to sustain communication. The pasture, of course, has rocks and trees that disrupt the communication but the cows have purchased diagonal mirrors ('/' and '\"' below) that deflect the laser beam through a 90 degree turn. Below is a map that illustrates the
problem.
H is 8 and W is 7 for this map. The two communicating cows are notated as 'C's; rocks and other blocking elements are notated as '*'s:
7 . . . . . . .         7 . . . . . . . 
6 . . . . . . C         6 . . . . . /-C 
5 . . . . . . *         5 . . . . . | * 
4 * * * * * . *         4 * * * * * | * 
3 . . . . * . .         3 . . . . * | . 
2 . . . . * . .         2 . . . . * | . 
1 . C . . * . .         1 . C . . * | . 
0 . . . . . . .         0 . \"-------/ . 
0 1 2 3 4 5 6           0 1 2 3 4 5 6 
Determine the minimum number of mirrors M that must be installed to maintain laser communication between the two cows, a feat which is always possible in the given test data.
奶牛们都改用激光进行通讯了.
在W*H的牧场上，一些地方有树木和石头遮挡激光，所以，奶 牛打算使用对角镜来进行激光通讯.两只奶牛的位置是固定的，对角镜能把光线旋转90度.

输入格式：

Line 1: Two space separated integers: W and H
Lines 2..H+1: The entire pasture.

输出格式：

Line 1: A single integer: M

输入样例#1：

7 8 
....... 
......C 
......* 
*****.* 
....*.. 
....*.. 
.C..*.. 
....... 

输出样例#1：

3