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: # coding: utf-8
def check(p):
    global ans
    global field
    ans+=1
    if(field[p[1]][p[0]]=='.'):
        field[p[1]][p[0]]='#'
    if(0<=p[0]+1<w and field[p[1]][p[0]+1]=='.'):
        check((p[0]+1,p[1]))
    if(0<=p[0]-1<w and field[p[1]][p[0]-1]=='.'):
        check((p[0]-1,p[1]))
    if(0<=p[1]+1<h and field[p[1]+1][p[0]]=='.'):
        check((p[0],p[1]+1))
    if(0<=p[1]-1<h and field[p[1]-1][p[0]]=='.'):
        check((p[0],p[1]-1))
    
    
while 1:
    ans=0
    w,h=map(int,input().split())
    if w==0:
        break
    field=[]
    for i in range(h):
        s=input()
        t=s.find('@')
        if(t!=-1):
            st=(t,i)
        field.append(list(s))
    check(st)
    print(ans)

Python: dxy = [[1,0],[-1,0],[0,1],[0,-1]]
n=0
def rec(x,y):
    global n
    if (x<0 or x>=h or y<0 or y>=w) or (visited[x][y] or tile[x][y]!='.'):
        return 0
    visited[x][y] = True
    n += 1
    for (dx,dy) in dxy:
        x2 = x + dx
        y2 = y + dy
        rec(x2,y2)
    return 0

w,h=map(int,input().split())
ans = []
while((w,h)!=(0,0)):
    n=0
    tile = []
    for _ in range(h):
        tile.append(list(input()))
    visited = [[False] * w for _ in range(h)]
    for a in range(h):
        for b in range(w):
            if(tile[a][b]=='@'):
                pos_x = a
                pos_y = b
                tile[a][b]='.'
    rec(pos_x, pos_y)
    ans.append(n)
    w,h=map(int,input().split())
for a in ans:
    print(a)

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)
with open("input1.txt") as f:
    width,height = [int(n) for n in f.readline().split(" ")]
    global lab
    while True:
        lab,start = [],[]
        for a in range(height):
            disp = [n for n in f.readline().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 f.readline().split(" ")]
            if width == 0 and height == 0:
                break

Python: if __name__ == "__main__":
    while 1:
        w,h = list(map(int,input().strip().split()))
        if w == h == 0:break
        data = []
        data = []
        for _ in range(h):data.append(list(input()))
        visited = []
        for i in range(h):
            if '@'in data[i]:stack= [(i,data[i].index('@'))]
        count = 0
        while len(stack) !=0:
            y,x= stack.pop()
            count +=1
            if y-1 >= 0 and not (y-1,x)in visited and data[y -1][x] == '.':
                visited.append((y-1,x))
                stack.append((y-1,x))
            if x -1 >= 0 and not (y,x-1)in visited and data[y][x-1] == '.':
                visited.append((y,x-1))
                stack.append((y,x-1))
            if y +1 < h and not (y+1,x)in visited and data[y +1][x] == '.':
                visited.append((y+1,x))
                stack.append((y+1,x))
            if x + 1 < w and not (y,x+1)in visited and data[y][x +1] == '.':
                visited.append((y,x+1))
                stack.append((y,x+1))

Python: 
while True:
    W, H = [int(n) for n in input().split()]

    if W == H == 0:
        break

    next_target = []

    room = []
    for n in range(H):
        s = list(input())
        room.append(s)
        for y in range(W):
            if s[y] == '@':
                next_target.append((n, y))

    result = 0

    while len(next_target) > 0:
        t = next_target.pop()

        # ???
        if t[0] - 1 >= 0 and room[t[0] - 1][t[1]] == '.':
            next_target.append((t[0] - 1, t[1]))
            room[t[0] - 1][t[1]] = '@'

        # ???
        if t[1] + 1 < W and room[t[0]][t[1] + 1] == '.':
            next_target.append((t[0], t[1] + 1))
            room[t[0]][t[1] + 1] = '@'

        # ???
        if t[0] + 1 < H and room[t[0] + 1][t[1]] == '.':
            next_target.append((t[0] + 1, t[1]))
            room[t[0] + 1][t[1]] = '@'

        # ???
        if t[1] - 1 >= 0 and room[t[0]][t[1] - 1] == '.':
            next_target.append((t[0], t[1] - 1))
            room[t[0]][t[1] - 1] = '@'

        # ?????????????????????????????????
        result += 1

    print(result)