import sys
from collections import deque

def debug(x, table):
    for name, val in table.items():
        if x is val:
            print('DEBUG:{} -> {}'.format(name, val), file=sys.stderr)
            return None

def solve():
    W, H = map(int, input().split())
    C = [list(input()) for i in range(H)]
    col = 1

    for i in range(H):
        for j in range(W):
            if C[i][j] == '#':
                C[i][j] = 0
            elif C[i][j] == '.':
                bfs_color(W, H, C, i, j, col)
                col += 1
            else:
                pass


    cave1 = []
    cave2 = []

    for i in range(H):
        for j in range(W):
            if C[i][j] == 1:
                cave1.append((i, j))
            elif C[i][j] == 2:
                cave2.append((i, j))

    min_d = 1000

    for a in cave1:
        for b in cave2:
            min_d = min(min_d, dist(a, b) - 1)

    print(min_d)


def dist(a, b):
    return abs(a[0] - b[0]) + abs(a[1] - b[1])


def bfs_color(W, H, C, i, j, col):
    nxt = deque([(i, j)])

    while nxt:
        y, x = nxt.pop()
        C[y][x] = col
        if x - 1 >= 0 and C[y][x-1] == '.':
            nxt.append((y, x-1))
        if x + 1 < W and C[y][x+1] == '.':
            nxt.append((y, x+1))
        if y - 1 >= 0 and C[y-1][x] == '.':
            nxt.append((y-1, x))
        if y + 1 < H and C[y+1][x] == '.':
            nxt.append((y+1, x))

    return None


if __name__ == '__main__':
    solve()