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: mx = [0, 1, 0, -1]
my = [-1, 0, 1, 0]

while True:
    w, h = map(int, input().split())
    if w == h == 0:
        break
    tiles = [[i for i in input()] for j in range(h)]
    ax = ay = 0
    for i in range(h):
        for j in range(w):
            if tiles[i][j] == '@':
                ax, ay = j, i
    que = [(ax, ay)]
    tiles[ay][ax] = '#'
    cnt = 1

    while 0 < len(que):
        new_que = []
        for x, y in que:
            for i in range(4):
                nx, ny = x + mx[i], y + my[i]
                if 0 <= nx <= w - 1 and 0 <= ny <= h - 1:
                    if tiles[ny][nx] == '.':
                        cnt += 1
                        new_que.append((nx, ny))
                        tiles[ny][nx] = '#'
        que = new_que
    print(cnt)

Python: w,h=map(int,input().split())
while w!=0 or h!=0:
    maps=[]
    flag=False
    ans=0
    for i in range(h):
        k=list(input())
        maps.append(k)
    for i in range(h):
        if flag:
            break
        for j in range(w):
            if maps[i][j]=='@':
                maps[i][j]='#'
                pos_x=i
                pos_y=j
                flag=True
                break
    def check(x,y):
        global maps
        if 0<=x<h and 0<=y<w:
            pass
        else:
            return False
        if maps[x][y]=='#':
            return False
        else:
            return True
    def bfs(x,y):
        global ans
        global maps
        for i in [[0,1],[0,-1],[1,0],[-1,0]]:
            p=i[0]
            q=i[1]
            if check(x+p,y+q):
                ans+=1
                maps[x+p][y+q]='#'
                bfs(x+p,y+q)
    bfs(pos_x,pos_y)
    print(ans+1)
    w,h=map(int,input().split())

Python: (lambda f: f(f))(lambda this, atin=lambda line, yp, ri=lambda l: room.append([{xi: x} for xi, x in enumerate(l)]): [point.__setitem__("x", line.index("@")), point.__setitem__("y", yp), ri(line)] if "@" in line else ri(line), search=lambda xpoint, ypoint, srch, now: [room[ypoint][xpoint].__setitem__(xpoint, "@"), srch(xpoint - 1, ypoint, srch, now) + srch(xpoint + 1, ypoint, srch, now) + srch(xpoint, ypoint + 1, srch, now) + srch(xpoint, ypoint - 1, srch, now) + 1][1] if 0 <= xpoint < wh[0] and 0 <= ypoint < wh[1] and now(xpoint, ypoint) else 0, now=lambda xpoint, ypoint: room[ypoint][xpoint].get(xpoint) is ".": [globals().__setitem__("wh", list(map(int, input().split()))), globals().__setitem__("room", []), globals().__setitem__("point", {"x": None, "y": None}), [atin(input(), ypoint) for ypoint in range(wh[1])], [room[point["y"]][point["x"]].__setitem__(point["x"], "."), print(search(point["x"], point["y"], search, now)), this(this)] if room else None])

Python: def main():
    while 1:
        w, h = map(int, input().split())
        if w == 0: break
        fld = [[] for i in range(h)]
        for i in range(h):
            readline = input()
            for j in range(w):
                item = readline[j]
                fld[i].append(item)
                if item == '@': sy, sx = i, j
        solve(fld, sy, sx)
        count = 0
        for i in range(h):
            for j in range(w):
                if fld[i][j] == 'A': count += 1
        print(count)

def solve(fld, cy, cx):
    vy = [1,-1,0,0]
    vx = [0,0,1,-1]
    fld[cy][cx] = 'A'
    for i in range(4):
        ny = cy + vy[i]
        nx = cx + vx[i]
        if ny < 0 or nx < 0 or ny >= len(fld) or nx >= len(fld[0]):continue
        elif fld[ny][nx] == '.': solve(fld, ny, nx)
main()

Python: from collections import deque

ans = []
while True:
    w, h = map(int, input().split())
    if not w and not h:
        break
    
    roadmap = []
    d = deque()
    able = [[False for i in range(w)] for j in range(h)]
    for i in range(h):
        roadmap.append(input())
        
    
    for i in range(h):
        for j in range(w):
            if roadmap[i][j] == '@':
                able[i][j] = True
                d.append([i, j])

    
    while len(d):
        y, x = d.pop()
        
        for course in [[0, 1], [1, 0], [-1, 0], [0, -1]]:
            tmpy, tmpx = y + course[0], x + course[1]
            if tmpy < 0 or tmpy >= h or tmpx < 0 or tmpx >= w:
                continue
                
            if not able[tmpy][tmpx] and roadmap[tmpy][tmpx] == '.':
                able[tmpy][tmpx] = True
                d.append([tmpy, tmpx])

    a = 0
    for i in range(h):
        a += len(list(filter(lambda x:x, able[i])))

    ans.append(a)

[print(i) for i in ans]