from collections import deque
import numpy as np
import sys

H, W = map(int, input().split())

Map = [[] for _ in range(H)]
reached = [[False] * W for _ in range(H)]
q = deque()
cnt = 0
count = 0
tempList = []
for y in range(H):
    for i, x in enumerate(input()):
        Map[y].append(x)
        if x == "#":
            cnt += 1
            reached[y][i] = True
            if i + 1 < W and not reached[y][i + 1]:
                reached[y][i + 1] = True
                tempList.append((i + 1, y))

            if i - 1 >= 0 and not reached[y][i - 1]:
                reached[y][i - 1] = True
                tempList.append((i - 1, y))

            if y + 1 < H and not reached[y + 1][i]:
                reached[y + 1][i] = True
                tempList.append((i, y + 1))

            if y - 1 >= 0 and not reached[y - 1][i]:
                reached[y - 1][i] = True
                tempList.append((i, y - 1))

q.append(tempList)


def BFS(blist):
    global count
    global cnt
    tList = []

    count += 1

    for (x, y) in blist:
        reached[y][x] = True
        Map[y][x] = "#"

        if x+1<W and not reached[y][x + 1]:
            tList.append((x + 1, y))

        if x-1>=0 and not reached[y][x - 1]:
            tList.append((x - 1, y))

        if y+1<H and not reached[y + 1][x]:
            tList.append((x, y + 1))

        if y-1>=0 and not reached[y - 1][x]:
            tList.append((x, y - 1))

    # if np.array(reached).all():
    #     print(count)
    #     sys.exit()
    if tList:
        q.append(tList)


while q:
    BFS(q.popleft())

print(count)













### FIXED CODE ###

from collections import deque

H, W = map(int, input().split())

Map = [[] for _ in range(H)]
reached = [[False] * W for _ in range(H)]
q = deque()
cnt = 0
count = 0
tempList = []
for y in range(H):
    for i, x in enumerate(input()):
        Map[y].append(x)
        if x == "#":
            cnt += 1
            reached[y][i] = True
            if i + 1 < W and not reached[y][i + 1]:
                reached[y][i + 1] = True
                tempList.append((i + 1, y))

            if i > 0 and not reached[y][i - 1]:
                reached[y][i - 1] = True
                tempList.append((i - 1, y))

            if y + 1 < H and not reached[y + 1][i]:
                reached[y + 1][i] = True
                tempList.append((i, y + 1))

            if y > 0 and not reached[y - 1][i]:
                reached[y - 1][i] = True
                tempList.append((i, y - 1))
if cnt==H*W:
    print(0)
    exit()

q.append(tempList)


def BFS(blist):
    global count
    tList = []

    count += 1

    for (x, y) in blist:
        if x+1<W and not reached[y][x + 1]:
            reached[y][x + 1] = True
            tList.append((x + 1, y))

        if x-1>=0 and not reached[y][x - 1]:
            reached[y][x - 1] = True
            tList.append((x - 1, y))

        if y+1<H and not reached[y + 1][x]:
            reached[y + 1][x] = True
            tList.append((x, y + 1))

        if y-1>=0 and not reached[y - 1][x]:
            reached[y - 1][x] = True
            tList.append((x, y - 1))

    if tList:
        q.append(tList)


while q:
    BFS(q.popleft())

print(count)