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: move = [[0, 1], [0, -1], [1, 0], [-1, 0]]
from collections import deque
def main(w, h):
    field = [list(input()) for i in range(h)]
    check = [[True] * w for i in range(h)]
    q = deque()
    for i in range(h):
        for k in range(w):
            if field[i][k] == "@":
                q.append((k, i))
                check[i][k] = False
    ans = 1
    while q:
        x, y = q.popleft()
        for mx, my in move:
            xm = mx + x
            ym = my + y
            if 0 <= xm < w and 0 <= ym < h:
                if field[ym][xm] == "." and check[ym][xm]:
                    check[ym][xm] = False
                    q.append((xm, ym))
                    ans += 1
    print(ans)
while 1:
    w, h = map(int, input().split())
    if w == h == 0:
        break
    main(w,h)

Python: from collections import deque
while 1:
    W,H = map(int,input().split())
    if W==0 and H==0:break
    tizu = []
    for i in range(H):
        row = input()
        if "@" in row:
            start = (i,row.index("@"))#h,w の順
        tizu.append(row)
    went = [[False]*W for i in range(H)]
    went[start[0]][start[1]] = True
    ans = 1
    queue = deque()#append,popleft
    queue.append(start)
    while queue:
        curh,curw = queue.popleft()
        for dh,dw in ((0,1),(0,-1),(1,0),(-1,0)):
            newh = curh + dh
            neww = curw + dw
            if 0<=newh<H and 0<=neww<W:
                if tizu[newh][neww] == "." and not went[newh][neww]:
                    went[newh][neww] =True
                    queue.append((newh,neww))
                    ans += 1
    print(ans)

Python: import queue
dxy=[(1,0),(0,1),(-1,0),(0,-1)]
def bfs(sx,sy,H,W):#幅優先探索
    q=queue.Queue()
    visited=[[False]*W for _ in range(H)]
    q.put((sx,sy))
    visited[sx][sy]=True
    ans=1
    while not q.empty():
        px,py=q.get()
        for dx,dy in dxy:
            nx=px+dx
            ny=py+dy
            if 0<=nx<H and 0<=ny<W:
                if c[nx][ny]=='.' and visited[nx][ny]==False:
                    visited[nx][ny]=True
                    q.put((nx,ny))
                    ans+=1
    return ans
while True:
    W,H=map(int,input().split())
    if(W==0 and H==0):
        break
    c=[input() for _ in range(H)]
    for i in range(H):
        if "@" in c[i]:
            sx=i
            sy=c[i].index("@")
    print(bfs(sx,sy,H,W))

Python: # -*- coding: utf-8 -*-
#rea and blac
h,w=1,1

count=0

def search(x,y):
    #マップの外側か壁の場合は何もしない
    #print(x,y)
    global count
    if x<0 or x>w-1 or y<0 or y>h-1 or map_data[y][x]=='#':
 
        return
        
    
    #以前に到達していたら何もしない
    if reached[y][x]:
         return

    reached[y][x]=1
    count+=1
    #print("aa")



    search(x+1,y)#右
    search(x-1,y)#左
    search(x,y+1)#上
    search(x,y-1)#下
    



while h!=0 and w!=0: 

    count=0
    #グラフの入力方法------

    w,h=map(int ,raw_input().split())
    if h==0 and w==0:
        break

    map_data = [[0]*w for _ in range(h)]
    reached = [[0]*w for _ in range(h)]
    for i in range(h):
        ct = raw_input()
        #print(len(ct))
        for j in range(w):
            map_data[i][j] = ct[j]
            if ct[j]=="@":
                sx=j
                sy=i

    #------



    search(sx,sy)

    print(count)
    count=0
    w=1
    h=1

Python: x=0
y=0
b=[]
t=[]
dir=[[1,0],[0,1],[-1,0],[0,-1]]
ans=0

def dfs(p_x,p_y):
  global b,t,ans
  if t[p_y][p_x] or not b[p_y][p_x]: return
  ans+=1
  t[p_y][p_x]=True
  for i in dir:
    dfs(p_x+i[0],p_y+i[1])

while True:
  x=0
  y=0
  w,h=map(int,input().split())
  if w==0 and h==0: break
  b=[[False]*(w+2) for i in range(h+2)]
  t=[[False]*(w+2) for i in range(h+2)]
  ans=0
  for i in range(1,h+1):
    tmp=list(input())
    for j in range(1,w+1):
      b[i][j]=(tmp[j-1] in {'.','@'})
      if tmp[j-1]=='@': x=j;y=i
  dfs(x,y)
  print(ans)

Python: from collections import deque

def solve(W, H, field):
    dire = [(1,0), (0,1), (-1,0), (0,-1)]
    for i in range(H):
        for j in range(W):
            if (field[i][j]=="@"):
                s = (i,j)
    check = [[0]*W for i in range(H)]
    q = deque()
    q.append(s)
    check[s[0]][s[1]] = 1
    ret = 1
    while q:
        y, x = q.popleft()
        for dy, dx in dire:
            if (y+dy<H) and (y+dy>=0) and (x+dx<W) and (x+dx>=0):
                if (field[y+dy][x+dx] == ".") and (not check[y+dy][x+dx]):
                    q.append((y+dy, x+dx))
                    check[y+dy][x+dx] = 1
                    ret += 1
    return ret

def main():
    ans = []
    while True:
        W, H = list(map(int, input().split()))
        if (not W) and (not H):
            break
        field = [input() for i in range(H)]
        ans.append(solve(W, H, field))
    for i in ans:
        print(i)
    
main()