from collections import deque
W,H = map(int,input().split())
C = [input().strip() for _ in range(H)]
A = [[100 for _ in range(W)] for _ in range(H)]
flag = 0
for i in range(H):
    for j in range(W):
        if C[i][j]==".":
            i0 = i
            j0 = j
            flag = 1
            break
    if flag==1:break
que = deque([(i0,j0,0)])
A[i0][j0]=0
while que:
    y,x,d = que.popleft()
    if x+1<W and C[y][x+1]==".":
        if A[y][x+1]>d:
            A[y][x+1]=d
            que.append((y,x+1,A[y][x+1]))
    elif x+1<W and C[y][x+1]=="#":
        if A[y][x+1]>d+1:
            A[y][x+1]=d+1
            que.append((y,x+1,d+1))
    if y-1>=0 and C[y-1][x]==".":
        if A[y-1][x]>d:
            A[y-1][x]=d
            que.append((y-1,x,d))
    elif y-1>=0 and C[y-1][x]=="#":
        if A[y-1][x]>d+1:
            A[y-1][x]=d+1
            que.append((y-1,x,d+1))
    if x-1>=0 and C[y][x-1]==".":
        if A[y][x-1]>d:
            A[y][x-1]=d
            que.append((y,x-1,d))
    elif x-1>=0 and C[y][x-1]=="#":
        if A[y][x-1]>d+1:
            A[y][x-1]=d+1
            que.append((y,x-1,d+1))
    if y+1<H and C[y+1][x]==".":
        if A[y+1][x]>d:
            A[y+1][x]=d
            que.append((y+1,x,d))
    elif y+1<H and C[y+1][x]=="#":
        if A[y+1][x]>d+1:
            A[y+1][x]=d+1
            que.append((y+1,x,d+1))
dmin = -1
for i in range(H):
    for j in range(W):
        if C[i][j]=="." and A[i][j]>0:
            dmin = A[i][j]
            break
    if dmin>0:break
print(dmin)