Machined Surfaces

An imaging device furnishes digital images of two machined surfaces that eventually will be assembled in contact with each other. The roughness of this final contact is to be estimated.

A digital image is composed of the two characters, "X" and " " (space). There are always 25 columns to an image, but the number of rows, N, is variable. Column one (1) will always have an "X" in it and will be part of the left surface. The left surface can extend to the right from column one (1) as contiguous X's.

Similarly, column 25 will always have an "X" in it and will be part of the right surface. The right surface can extend to the left from column 25 as contiguous X's.

Digital-Image View of Surfaces

 Left                                Right
XXXX                                               XXXXX
XXX                                              XXXXXXX
XXXXX                                               XXXX
XX                                                XXXXXX
. .
. .
. .
XXXX                                                 XXXX
XXX                                                 XXXXXX
1 25

In each row of the image, there can be zero or more space characters separating the left surface from the right surface. There will never be more than a single blank region in any row.

For each image given, you are to determine the total ``void" that will exist after the left surface has been brought into contact with the right surface. The ``void" is the total count of the spaces that remains between the left and right surfaces after theyhave been brought into contact.

The two surfaces are brought into contact by displacing them strictly horizontally towards each other until a rightmost "X" of the left surface of some row is immediately to the left of the leftmost "X" of the right surface of that row. There is no rotation or twisting of these two surfaces as they are brought into contact; they remain rigid, and only move horizontally.

Note: The original image may show the two surfaces already in contact, in which case no displacement enters into the contact roughness estimation.

Input

The input consists of a series of digital images. Each image data set has the following format:

First line -A single unsigned integer, N, with value greater than zero (0) and less than 13. The first digit of N will be the first character on a line.

Next N lines -Each line has exactly 25 characters; one or more X's, then zero or more spaces, then one or more X's.

The end of data is signaled by a null data set having a zero on the first line of an image data set and no further data.

Output

For each image you receive as a data set, you are to reply with the total void (count of spaces remaining after the surfaces are brought into contact). Use the default output for a single integer on a line.

Sample Input (character "B" for ease of reading. The actual input file will use the ASCII-space character, not "B").

4XXXXBBBBBBBBBBBBBBBBXXXXXXXXBBBBBBBBBBBBBBBXXXXXXXXXXXXBBBBBBBBBBBBBBBBXXXXXXBBBBBBBBBBBBBBBBBXXXXXX2XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX1XXXXXXXXXBBBBBBBBBBBBBBXX0

Sample Output

40
0
其实看到这个题的时候，当场就跪了。
怎么看懂呢？光看题是不行的，一定要结合图来看，这个图其实原来是有错误的，现在没了。
大概意思是说，第一数字大家应该都知道怎么写，用EOF就行，接下来是，几组数据
（注意B只是方便大家看数量，最后还是要换成空格的，这里隐含的意思是说应定要用gets，不能用scanf，把左边或者右边的X看成一个整体，来向左移动（这4组都移），第一步把X移动完了，开始移  动（可视为删除）空格了，直到其中一个句子的空格没有了结束，然后看一下，这几个句子还剩下几个空格。
其实这就是道水题，算法很简单，但是题意很难理解。
#include<stdio.h>#include<string.h>int main(){char a[30];int i,n,j,s,k,min;while(scanf("%d",&n)!=EOF){if(!n)break;s=0;min=1000;getchar();for(k=1;k<=n;k++){j=0;i=0;gets(a);while(a[i]!='\0'){if(a[i]==' ')j++;i++;}s+=j;if(j<min)min=j;}printf("%d\n",s-n*min);}return 0;}