# [Usaco2005 jan]Muddy Fields 泥泞的牧场

时间限制：5s 空间限制：64MB

### 题目描述

Rain has pummeled the cows' field, a rectangular grid of R rows and C columns (1 <= R <= 50, 1 <= C <= 50). While good for the grass, the rain makes some patches of bare earth quite muddy. The cows, being meticulous grazers, don't want to get their hooves dirty while they eat. To prevent those muddy hooves, Farmer John will place a number of wooden boards over the muddy parts of the cows' field. Each of the boards is 1 unit wide, and can be any length long. Each board must be aligned parallel to one of the sides of the field. Farmer John wishes to minimize the number of boards needed to cover the muddy spots, some of which might require more than one board to cover. The boards may not cover any grass and deprive the cows of grazing area but they can overlap each other. Compute the minimum number of boards FJ requires to cover all the mud in the field.

### 输入格式

* Line 1: Two space-separated integers: R and C

* Lines 2..R+1: Each line contains a string of C characters, with '*' representing a muddy patch, and '.' representing a grassy patch. No spaces are present.

第1行：两个整数R和C.

第2到R+1行：每行C个字符，其中“*’代表泥地，“．”代表草地．

### 输出格式

* Line 1: A single integer representing the number of boards FJ needs.

最少需要多少木板．

### 样例输入

4 4 *.*. .*** ***. ..*.

### 样例输出

4

### 提示

### 题目来源

Gold