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: import sys
sys.setrecursionlimit(10000000)
MOD = 10 ** 9 + 7
INF = 10 ** 15
Dy = (-1,0,1,0)
Dx = (0,1,0,-1)

from collections import deque,defaultdict,Counter
def solve(H,W):
    grid = [input() for _ in range(H)]
    cnt = [[0]*W for _ in range(H)]
    for i in range(H):
        for j in range(W):
            if grid[i][j] == '@':
                sy,sx = i,j
                break
    
    q = deque([(sy,sx)])
    cnt[sy][sx] = 1
    ans = 1
    while q:
        ny,nx = q.popleft()
        for dy,dx in zip(Dy,Dx):
            y = ny + dy
            x = nx + dx
            if y < 0 or y >= H:
                continue
            if x < 0 or x >= W:
                continue
            if grid[y][x] == '#':
                continue
            if cnt[y][x] == 1:
                continue
            cnt[y][x] = 1
            ans += 1
            q.append((y,x))
    print(ans)
    
def main():
    while True:
        W,H = map(int,input().split())
        if H == 0 and W == 0:
            return
        solve(H,W)
if __name__ == '__main__':
    main()

Python: def solve(w,h,tile):
    # 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])
    return count

while True:
    try:
        w, h = map(int, input().split())
        if w == 0:
            break
        tile = [""] * h
        for i in range(h):
            tile[i] = input()

        print(solve(w,h,tile))
    except:
        break

Python: adjR = [-1, 0, 0, 1]
adjC = [0, 1, -1, 0]

def isValid(row, col, ROWS, COLS):
    return row >= 0 and row < ROWS and col >= 0 and col < COLS

def floodfill(board, row, col, ROWS, COLS):
    global adjR
    global adjC

    if not isValid(row, col, ROWS, COLS):
        return 0
    if board[row][col] == '#':
        return 0

    board[row][col] = '#'
    total = 1
    for x in range(4):
        rr = row + adjR[x]
        cc = col + adjC[x]
        total += floodfill(board, rr, cc, ROWS, COLS)
    return total
    

if __name__ == '__main__':
    while True:
        COLS, ROWS = list(map(int, input().split()))
        if ROWS == 0 and COLS == 0:
            break

        board = []
        for i in range(ROWS):
            line = input()
            board.append([ c for c in line ])
            if '@' in line:
                row = i
                col = line.find('@')
        
        print(  floodfill(board, row, col, ROWS, COLS)  )

Python: while True:
    w, h = map(int, input().split())
    if w == 0:
        break
    a = []
    for i in range(h):
        t = list(input())
        a.append(t)
        if '@' in t:
            x = i
            y = t.index('@')
    stk = [[x, y]]
    c = 1
    while True:
        if stk == []:
            break
        x, y = stk.pop()
        if y != w-1 and a[x][y+1] == '.':
            a[x][y+1] = '@'
            stk.append([x, y+1])
        if y != 0 and a[x][y-1] == '.':
            a[x][y-1] = '@'
            stk.append([x, y-1])
        if x != h-1 and a[x+1][y] == '.':
            a[x+1][y] = '@'
            stk.append([x+1, y])
        if x != 0 and a[x-1][y] == '.':
            a[x-1][y] = '@'
            stk.append([x-1, y])
    print(sum([t.count('@') for t in a]))

Python: def f(h,w):
  global W,H,S,A
  if h<0 or h>=H or w<0 or w>=W or S[h][w]=="#" or A[h][w]==1:
    return
  A[h][w] = 1
  f(h-1,w)
  f(h+1,w)
  f(h,w-1)
  f(h,w+1)
while True:
  W,H = map(int,input().split())
  if W+H == 0:
    break
  S = [list(input()) for h in range(H)]
  A = [[0 for w in range(W)] for h in range(H)]
  for h in range(H):
    for w in range(W):
      if S[h][w] == "@":
        f(h,w)
        break
  ans = 0
  for i in A:
    ans += sum(i)
  print(ans)

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: h=0
w=0

while 1:
    w,h=map(int,input().split())
    if h==0 and w==0:
        break
    grid=[]
    sx=-1
    sy=-1
    ans=1
    used=[[0]*w for i in range(h)]
    def valid(i,j):
        return i>=0 and j>=0 and i<h and j<w and grid[i][j]=='.' and not used[i][j]
    for i in range(h):
        row=input()
        grid.append(row)
        for j in range(w):
            if row[j]=='@':
                sx=i
                sy=j
    stk=[(sx,sy)]
    while stk:
        x=stk[-1][0]
        y=stk[-1][1]
        stk.pop()
        for d in [(1,0),(0,1),(-1,0),(0,-1)]:
            xx=x+d[0]
            yy=y+d[1]
            if valid(xx,yy):
                stk.append((xx,yy))
                used[xx][yy]=1
                ans+=1
    print(ans)