## Red and Black

There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can’t move on red tiles, he can move only on black tiles.
Write a program to count the number of black tiles which he can reach by repeating the moves described above.

Input
The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.
There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.

‘.’ - a black tile
‘#’ - a red tile
‘@’ - a man on a black tile(appears exactly once in a data set)

Output
For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).

**Sample Inpu**t
6 9
….#.
…..#
……
……
……
……
……
#
@…#
.#..#.

11 9
.#………
.#.#######.
.#.#…..#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#…….#.
.#########.

………..
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..

7 7
..#.#..
..#.#..

…@…

### .

..#.#..
..#.#..
0 0

Sample Output
45
59
6
13

``````#include<stdio.h>
#include<cstdio>
#include<bits/stdc++.h>
const int  MAX=50;
int ans,w,k;
char a[MAX][MAX];
int vis[MAX][MAX];
int d[2][4]={{1,-1,0,0},{0,0,1,-1}};
void DFS(int x,int y)
{
vis[x][y]=1;
ans++;
for(int i=0;i<4;i++)
{
int dx = x + d[0][i];
int dy = y + d[1][i];
if(dx>=0&&dx<k&&dy>=0&&dy<w&&vis[dx][dy]!=1&&a[dx][dy]!='#')
DFS(dx,dy);
}
}
int main()
{
int i,j;
while(~scanf("%d%d",&w,&k)&&(w+k)!=0)  //k行w列
{   memset(vis,0,sizeof(vis));
ans=0;
for(i=0;i<k;i++)
{
scanf("%s",a[i]);
}
for(i=0;i<k;i++)
{
for(j=0;j<w;j++)
if(a[i][j]=='@')
{   DFS(i,j);
break;
}
}
printf("%d\n",ans);
}
return 0;
}``````