Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

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

type Color int

const (
	ColorBlack Color = iota
	ColorRed
)

type Node struct {
	ID    int
	X, Y  int
	Color Color
	Nexts []*Node
}

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])

		// Initialize map
		m := map[int]map[int]*Node{}
		for x := 1; x <= w; x++ {
			m[x] = map[int]*Node{}
			for y := 1; y <= h; y++ {
				m[x][y] = &Node{ID: x + y*w, X: x, Y: y}
			}
		}
		for x := 1; x <= w; x++ {
			for y := 1; y <= h; y++ {
				nexts := []*Node{}
				if n, ok := m[x-1][y]; ok {
					nexts = append(nexts, n)
				}
				if n, ok := m[x][y-1]; ok {
					nexts = append(nexts, n)
				}
				if n, ok := m[x+1][y]; ok {
					nexts = append(nexts, n)
				}
				if n, ok := m[x][y+1]; ok {
					nexts = append(nexts, n)
				}
				m[x][y].Nexts = nexts
			}
		}

		// Set colors
		queue := []*Node{}
		touchedIDs := map[int]struct{}{}
		for y := 1; y <= h; y++ {
			sc.Scan()
			for i, c := range sc.Text() {
				switch c {
				case '.', '@':
					n := m[i+1][y]
					n.Color = ColorBlack
					if c == '@' {
						queue = append(queue, n)
						touchedIDs[n.ID] = struct{}{}
					}
				case '#':
					m[i+1][y].Color = ColorRed
				}
			}
		}

		// Search
		visitedIDs := map[int]struct{}{}
		for {
			if len(queue) == 0 {
				break
			}
			n := queue[0]
			queue = queue[1:]
			visitedIDs[n.ID] = struct{}{}
			for _, next := range n.Nexts {
				if next.Color == ColorRed {
					continue
				}
				if _, ok := touchedIDs[next.ID]; !ok {
					queue = append(queue, next)
					touchedIDs[n.ID] = struct{}{}
				}
			}
		}
		fmt.Println(len(visitedIDs))
	}
}

Python: def dfs(now,origin,drawn): # 深さ優先探索　再帰関数　originは変更しない　drawnは訪れた場所に1それ以外は0
    positive = '.' # 進める場所
    negative = '#' # 進めない場所(壁)
    direct = [0,0,0,0] # [上,下,左,右]を表す
    height = len(origin)
    width = len(origin[0])
    now_h = now[0]
    now_w = now[1]
    ### それぞれの方向について、originにおいてpositiveかつdrawnにおいて0（つまり訪れたことがある）なら進める
    if now_h != 0 and origin[now_h-1][now_w] == positive and drawn[now_h-1][now_w] == 0:
        direct[0] = 1
    if now_h != height-1 and origin[now_h+1][now_w] == positive and drawn[now_h+1][now_w] == 0:
        direct[1] = 1
    if now_w != 0 and origin[now_h][now_w-1] == positive and drawn[now_h][now_w-1] == 0:
        direct[2] = 1
    if now_w != width-1 and origin[now_h][now_w+1] == positive and drawn[now_h][now_w+1] == 0:
        direct[3] = 1

    if sum(direct) == 0: # 進む先がなければ終了
        return 0
    d = {0:[now_h-1,now_w],1:[now_h+1,now_w],2:[now_h,now_w-1],3:[now_h,now_w+1]} # 進む先の座標を辞書にしておく
    for i in range(4):
        if direct[i] == 1:
            drawn[d[i][0]][d[i][1]] = 1 # d[i]の座標に移動したのでdrawnで訪れたことを記録した
            dfs(d[i],origin,drawn) # 再帰
    return 0

while True:
    W, H = map(int,input().split()) # 入力を受け取る
    if W == 0 and H == 0: # 両方0だったらbreak
        break
    tiles = [list(input()) for i in range(H)] # 入力
    possible_tiles = [[0 for i in range(W)] for j in range(H)] # 訪れたことがある場所を記憶する
    for h in range(H):
        for w in range(W):
            if tiles[h][w] == '@': # 現在地
                now = [h,w]
                break
    possible_tiles[now[0]][now[1]] = 1 # 現在地は既に訪れている
    dfs(now,tiles,possible_tiles) # 探索
    ans = 0
    for h in range(H):
        for w in range(W):
            if possible_tiles[h][w] == 1:
                ans += 1
    print(ans)

Python: import sys

cnt = 0

def solve():
    while 1:
        w, h = map(int, sys.stdin.readline().split())

        if w == h == 0:
            return

        room = [list(sys.stdin.readline().rstrip()) for i in range(h)]

        for i in range(h):
            if '@' in room[i]:
                si = i
                sj = room[i].index('@')
                break

        global cnt
        cnt = 0
        dfs(w, h, room, si, sj)
        print(cnt)

def dfs(w, h, room, i, j):
    if i < 0 or i >= h or j < 0 or j >= w or (room[i][j] == '#'):
        return

    global cnt
    cnt += 1
    room[i][j] = '#'

    dfs(w, h, room, i + 1, j)
    dfs(w, h, room, i - 1, j)
    dfs(w, h, room, i, j + 1)
    dfs(w, h, room, i, j - 1)

if __name__ == '__main__':
    solve()

Python: while True:
    W, H = map(int, input().split())
    if W == 0 and H == 0:
        break
    maze = []
    for _ in range(H):
        maze.append(list(input()))
    visited = [[False] * W for _ in range(H)]
    dxy = [(1, 0), (0, 1), (-1, 0), (0, -1)]
    ans = 0


    def rec(x, y):
        global ans
        visited[x][y] = True
        ans += 1
        for (dx, dy) in dxy:  # 4方向の移動を試す
            x2 = x + dx
            y2 = y + dy
            if 0 <= x2 < H and 0 <= y2 < W:
                if maze[x2][y2] == '.':
                    if not visited[x2][y2]:
                        rec(x2, y2)  # 再帰呼び出し


    for h in range(H):
        for w in range(W):
            if maze[h][w] == '@':
                rec(h, w)
                break
        else:
            continue
        break

    print(ans)

Python: while True:
    W,H = [int(x) for x in input().split()]
    if W==0 and H==0:
        exit()
    tiles = []
    X = 0
    Y = 0
    for i in range(H):
        tiles.append(input())
        if '@' in tiles[i]:
            Y = i
            X = tiles[i].index('@')
    d = [[9999 for j in range(H*W)] for i in range(H*W)]
    for i in range(H*W):
        d[i][i] = 0
    for i in range(H):
        for j in range(W):
            if j>0:
                if tiles[i][j] in '.@' and tiles[i][j-1] in '.@':
                    d[W*i+j][W*i+j-1] = 1
            if j<W-1:
                if tiles[i][j] in '.@' and tiles[i][j+1] in '.@':
                    d[W*i+j][W*i+j+1] = 1
            if i>0:
                if tiles[i][j] in '.@' and tiles[i-1][j] in '.@':
                    d[W*i+j][W*i+j-W] = 1
            if i<H-1:
                if tiles[i][j] in '.@' and tiles[i+1][j] in '.@':
                    d[W*i+j][W*i+j+W] = 1
    for k in range(H*W):
        for i in range(H*W):
            for j in range(H*W):
                if d[i][j] > d[i][k]+d[k][j]:
                    d[i][j] = d[i][k]+d[k][j]
    cnt = 0
    for i in range(H*W):
        if d[X+Y*W][i]<9999:
            cnt += 1
    print(cnt)

Python: (lambda f:f(f))(lambda T,A=lambda L,yp,ri=lambda l:R.append([{xi:x}for xi,x in enumerate(l)]):[P.__setitem__("x",L.index("@")),P.__setitem__("y",yp),ri(L)]if "@"in L else ri(L),S=lambda X,Y,s,u:[R[Y][X].__setitem__(X,"@"),s(X-1,Y,s,u)+s(X+1,Y,s,u)+s(X,Y+1,s,u)+s(X,Y-1,s,u)+1][1]if 0<=X<W[0]and 0<=Y<W[1]and u(X,Y)else 0,u=lambda X,Y:R[Y][X].get(X)is ".",g=globals:[g().__setitem__("W",list(map(int,input().split()))),g().__setitem__("R",[]),g().__setitem__("P",{"x":9,"y":9}),[A(input(),Y)for Y in range(W[1])],[R[P["y"]][P["x"]].__setitem__(P["x"],"."),print(S(P["x"],P["y"],S,u)),T(T)]if R else 9])

Python: while True:
    w, h = map(int, input().split())
    if w == 0:
        break
    # タイルの情報を文字列配列として受け取る
    tile = [""] * h
    for i in range(h):
        tile[i] = input()
    # スタート地点探索
    ok = False
    for y in range(h):
        for x in range(w):
            if tile[y][x] == "@":
                s_x = x
                s_y = y
                ok = True
                break
        if ok:
            break
    # 幅優先探索
    count = 0
    check = [[s_x, s_y]]
    check_map = [[False for j in range(w)] for i in range(h)]
    while len(check) > 0:
        x, y = check.pop(0)
        if x in range(w) and y in range(h):
            if check_map[y][x] == False:
                if tile[y][x] == "." or tile[y][x] == "@":
                    check_map[y][x] = True
                    count += 1
                    check.append([x, y-1])
                    check.append([x, y+1])
                    check.append([x+1, y])
                    check.append([x-1, y])
    print(count)