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.
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)
The end of the input is indicated by a line consisting of two zeros.
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).
- 二维矩阵中，有 '@'，'.'，'#'，三种字符，其中 @ 是起点，# 是红色，. 是黑色，求@连通的最大最色格子数目。@ 本身是黑色。
- dfs 连通图。