DFS

import java.io.*;
class Main{
    static BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
    static int N = 25, row, col;
    static char[][] a = new char[N][N];
    static int[][] dir = new int[][]{{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
    public static void main(String[] args) throws Exception{
        while(true){
            String[] ss = read.readLine().split(" ");
            row = Integer.valueOf(ss[1]);
            col = Integer.valueOf(ss[0]);
            if(row == 0 && col == 0) break;
            boolean[][] st = new boolean[row][col];
            int x = 0, y = 0;
            for(int i = 0; i < row; i++){
                String s = read.readLine();
                for(int j = 0; j < col; j++){
                    a[i][j] = s.charAt(j);
                    if(a[i][j] == '@'){
                        x = i; y = j;
                    }
                }
            }
            System.out.println(dfs(x, y, st));
        }
    }

    public static int dfs(int x, int y, boolean[][] st){
        int res = 1;
        st[x][y] = true;
        for(int i = 0; i < 4; i++){
            int nx = x + dir[i][0], ny = y + dir[i][1];
            if(nx < 0 || nx >= row || ny < 0 || ny >= col) continue;
            if(st[nx][ny] || a[nx][ny] == '#') continue;
            res += dfs(nx, ny, st);
        }
        return res;
    }
}

BFS

import java.io.*;
import java.util.*;
class Main{
    static BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
    static int N = 25;
    static char[][] a = new char[N][N];
    static int[][] dir = new int[][]{{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
    public static void main(String[] args) throws Exception{
        while(true){
            String[] ss = read.readLine().split(" ");
            int row = Integer.valueOf(ss[1]);
            int col = Integer.valueOf(ss[0]);
            if(row == 0 && col == 0) break;
            boolean[][] st = new boolean[row][col];
            Queue<int[]> q = new LinkedList();
            int x1 = 0, y1 = 0;
            for(int i = 0; i < row; i++){
                String s = read.readLine();
                for(int j = 0; j < col; j++){
                    a[i][j] = s.charAt(j);
                    if(a[i][j] == '@'){
                        x1 = i; y1 = j;
                    }
                }
            }
            int cnt = 0;
            st[x1][y1] = true;
            q.offer(new int[]{x1, y1});
            while(!q.isEmpty()){
                int[] poll = q.poll();
                cnt++;
                for(int i = 0; i < 4; i++){
                    int nx = dir[i][0] + poll[0];
                    int ny = dir[i][1] + poll[1];
                    if(nx < 0 || nx >= row || ny < 0 || ny >= col) continue;
                    if(st[nx][ny] || a[nx][ny] == '#') continue;
                    st[nx][ny] = true;
                    q.offer(new int[]{nx, ny});
                }
            }
            System.out.println(cnt);

        }
    }
}