HDU 1198 Farm Irrigation

Link:

http://acm.hdu.edu.cn/showproblem.php?pid=1198

Topic:

Problem Description

Benny has a spacious farm land to irrigate. The farm land is a rectangle, and are divided into a lot of samll squares. Water pipes are placed in these squares. Different square has a different type of pipe. There are types of pipes, which is marked from A to K, as Figure 1 shows.

Figure 1 Benny has a map of his farm, which was an array of marks denoting the distribution of water pipes over the whole F Arm. For example, if it has a map ADC fjk IHE then the water pipes the are like

Figure 2

Several wellsprings are found in the center of some squares, so water can flow along the pipes from one square to another. If water flow crosses one square, the whole farm land in this square is irrigated and would have a good harvest in autumn. Now Benny wants to know in least how many wellsprings is should to found the have of land whole. Can you help him? Note:in The above example, at least 3 wellsprings are needed, as those red points in Figure 2. Input

There are several test cases! In each test case, the contains 2 integers m and N, then M lines follow. In each of this lines, there are N characters, in the range of ' A ' to ' K ', denoting the type of water pipe over the Corre Sponding Square. A negative M or n denotes the end of input, else you can assume 1 <= M, n <= 50.

Output

For each test case, output in one line the least number of wellsprings needed.

Sample Input

2 2
DK
HF

3 3
ADC
fjk
IHE

-1-1

Sample Output

2
3