Go: package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"strconv"
	"strings"
)

var (
	sc = bufio.NewScanner(os.Stdin)
)

type Color int

const (
	ColorBlack Color = iota
	ColorRed
)

var strByColor = map[Color]string{
	ColorBlack: "black",
	ColorRed:   "red",
}

func (c Color) String() string {
	return strByColor[c]
}

type Node struct {
	ID      int
	X, Y    int
	Color   Color
	NextIDs map[int]struct{}
}

func (n *Node) String() string {
	d, _ := json.Marshal(n)
	return string(d)
}

type Map struct {
	Width, Height int
	Nodes         map[int]*Node
}

func (m *Map) GetByID(id int) *Node {
	return m.Nodes[id]
}

func (m *Map) Get(x, y int) *Node {
	return m.Nodes[m.getID(x, y)]
}

func (m *Map) SetColor(x, y int, c Color) {
	m.Nodes[m.getID(x, y)].Color = c
}

func (m *Map) getID(x, y int) int {
	return x + y*m.Width
}

func (m *Map) init() {
	for x := 1; x <= m.Width; x++ {
		for y := 1; y <= m.Height; y++ {
			id := m.getID(x, y)
			m.Nodes[id] = &Node{ID: id, X: x, Y: y}
		}
	}
	for x := 1; x <= m.Width; x++ {
		for y := 1; y <= m.Height; y++ {
			nextIDs := map[int]struct{}{}
			if x > 1 {
				nextIDs[m.getID(x-1, y)] = struct{}{}
			}
			if x < m.Width {
				nextIDs[m.getID(x+1, y)] = struct{}{}
			}
			if y > 1 {
				nextIDs[m.getID(x, y-1)] = struct{}{}
			}
			if y < m.Height {
				nextIDs[m.getID(x, y+1)] = struct{}{}
			}
			m.Get(x, y).NextIDs = nextIDs
		}
	}
}

func NewMap(w, h int) *Map {
	m := &Map{Width: w, Height: h, Nodes: map[int]*Node{}}
	m.init()
	return m
}

type Searcher struct {
	Map        *Map
	queue      []*Node
	touchedIDs map[int]struct{}
	visitedIDs map[int]struct{}
}

func NewSearcher(m *Map) *Searcher {
	return &Searcher{
		Map:        m,
		queue:      []*Node{},
		touchedIDs: map[int]struct{}{},
		visitedIDs: map[int]struct{}{},
	}
}

func (s *Searcher) Search(start *Node) {
	s.enqueue(start)

	for {
		if len(s.queue) == 0 {
			break
		}
		for nextID := range s.dequeue().NextIDs {
			n := s.Map.GetByID(nextID)
			if n.Color == ColorRed || s.hasTouched(n) {
				continue
			}
			s.enqueue(n)
		}
	}
}

func (s *Searcher) VisitedNodeCount() int {
	return len(s.visitedIDs)
}

func (s *Searcher) hasTouched(n *Node) bool {
	_, ok := s.touchedIDs[n.ID]
	return ok
}

func (s *Searcher) enqueue(n *Node) {
	s.queue = append(s.queue, n)
	s.touchedIDs[n.ID] = struct{}{}
}

func (s *Searcher) dequeue() *Node {
	n := s.queue[0]
	s.queue = s.queue[1:]
	s.visitedIDs[n.ID] = struct{}{}
	return n
}

func main() {
	for sc.Scan() {
		if sc.Text() == "0 0" {
			break
		}
		chunks := strings.Split(sc.Text(), " ")
		w, _ := strconv.Atoi(chunks[0])
		h, _ := strconv.Atoi(chunks[1])

		m := NewMap(w, h)

		// Set colors
		var start *Node
		for y := 1; y <= h; y++ {
			sc.Scan()
			for i, c := range sc.Text() {
				switch c {
				case '.', '@':
					m.SetColor(i+1, y, ColorBlack)
					if c == '@' {
						start = m.Get(i+1, y)
					}
				case '#':
					m.SetColor(i+1, y, ColorRed)
				}
			}
		}

		// Search
		s := NewSearcher(m)
		s.Search(start)
		fmt.Println(s.VisitedNodeCount())
	}
}

Python: from collections import deque

dx,dy = [1,0,-1,0],[0,1,0,-1]

while True:
	w,h = map(int,input().split())
	if w == 0 and h == 0:
		break
	field = [input() for i in range(h)]
	for i in range(h):
		if '@' in field[i]:
			sx,sy = i,field[i].find('@')
	visited = [[False for i in range(w)] for j in range(h)]
	que = deque()
	que.append((sx,sy))
	visited[sx][sy] = True
	while que:
		p = que.popleft()
		for i in range(4):
			nx,ny = p[0] + dx[i],p[1] + dy[i]
			if 0 <= nx < h and 0 <= ny < w and field[nx][ny] != '#' and not visited[nx][ny]:
				visited[nx][ny] = True
				que.append((nx,ny))
	cnt = 0
	for i in range(h):
		for j in range(w):
			cnt += visited[i][j]
	print(cnt)

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-

def dfs(s,Map,H,W):
    dxdy = [(1,0),(-1,0),(0,1),(0,-1)]
    for i in range(4):
        Map[s[0]][s[1]] = '*'
        nextPos = (s[0]+dxdy[i][0],s[1]+dxdy[i][1])
        if nextPos[0] >= 0 and nextPos[1] >= 0 and nextPos[0] < H and nextPos[1] < W:
            if Map[nextPos[0]][nextPos[1]] == '.':
                dfs(nextPos,Map,H,W)

while True:
    W,H = map(int,input().split(" "))
    if W == 0 and H == 0:
        break
    Map = [list(input()) for i in range(0,H)]
    for i in range(H):
        for j in range(W):
            if Map[i][j] == '@':
                S = (i,j)

    dfs(S,Map,H,W)
    print(sum([1 if Map[i][j] == '*' else 0 for i in range(H) for j in range(W)]))

Python: dxy = [(1, 0), (0, 1), (-1, 0), (0, -1)]
def rec(maze, visited, locat):
  # ４方向全て試す
  for i in dxy:
    n_locat = (locat[0] + i[0], locat[1] + i[1])
    if 0 <= n_locat[0] < len(maze) and 0 <= n_locat[1] < len(maze[0]):
      if maze[n_locat[0]][n_locat[1]] == '.':
        if visited[n_locat[0]][n_locat[1]] == False:
          global count 
          count += 1
          visited[n_locat[0]][n_locat[1]] = True
          rec(maze, visited, n_locat)
  return count
while(True):
  w, h = map(int, input().split())
  if w == 0 and h == 0:
    break
  maze = [[]for i in range(h)]
  visited = [[False for i in range(w)] for j in range(h)]
  for i in range(h):
    mazel = list(input())
    maze[i] = mazel
  count = 1 # @のいちを予めカウントしておく
  for i in range(h):
    for j in range(w):
      if maze[i][j] == '@':
        s = [i, j]
        break
    else:
      continue
    break
  print(rec(maze, visited, s))

Python: import queue

while True :
    w,h = map(int,input().split())
    if w==0 and h ==0 :
        break
    maze = [input() for _ in range(h)]
    visited = [[-1]*w for _ in range(h)]
    for i in range(h):
        if "@"  in  maze[i]:
            x_f = i
    for i in range(w):
        if maze[x_f][i] =="@":
            y_f = i
    visited[x_f][y_f] = 1
    q = queue.Queue()
    q.put([x_f,y_f])
    cnt  = 1
    while  not q.empty():
        x,y = q.get()
        for dx,dy in [(1,0),(-1,0),(0,1),(0,-1)]:
            if 0<= x+dx < h and 0<= y+dy < w:
                if visited[x+dx][y+dy] == -1 and maze[x+dx][y+dy]=='.':
                    cnt += 1
                    visited[x+dx][y+dy] = 1
                    q.put([x+dx,y+dy])
    print(cnt)

Python: def getter(targ,x,y):
    #print(x,y,len(targ[0]),len(targ))
    if 0 > x or x >= len(targ) or 0 > y or y >= len(targ[0]) or targ[x][y] == '#':
        return 0
    else:
        targ[x][y] = '#'
        return 1 + getter(targ,x+1,y) + getter(targ,x-1,y) + getter(targ,x,y+1) + getter(targ,x,y-1)
width,height = [int(n) for n in input().split(" ")]
global lab
while True:
    lab,start = [],[]
    for a in range(height):
        disp = [n for n in input().rstrip('\n')]
        if '@' in disp:
            start.extend([disp.index('@'),a])
        lab.append(disp)
    else:
        a,b = start
        print(getter(lab,b,a))
        width,height = [int(n) for n in input().split(" ")]
        if width == 0 and height == 0:
            break