import sys
input = sys.stdin.readline

H, W = map(int, input().split())
S = [input().rstrip() for _ in range(H)]

reachable1 = [[0] * W for _ in range(H)]
st = []
for i in range(H):
    for j in range(W):
        if S[i][j] == '#' and (i >= H-3 or j < 3):
            reachable1[i][j] = 1
            st.append((i, j))
while st:
    i, j = st.pop()
    for ni in range(i-3, i+4):
        for nj in range(j-3, j+4):
            if abs(i-ni)+abs(j-nj) <= 5 and 0 <= ni < H and 0 <= nj < W and S[ni][nj] == '#' and not reachable1[ni][nj]:
                reachable1[ni][nj] = 1
                st.append((ni, nj))


reachable2 = [[0] * W for _ in range(H)]
st = []
for i in range(H):
    for j in range(W):
        if S[i][j] == '#' and (i < 3 or j >= W-3):
            reachable2[i][j] = 1
            st.append((i, j))
while st:
    i, j = st.pop()
    for ni in range(i-3, i+4):
        for nj in range(j-3, j+4):
            if abs(i-ni)+abs(j-nj) <= 5 and 0 <= ni < H and 0 <= nj < W and S[ni][nj] == '#' and not reachable2[ni][nj]:
                reachable2[ni][nj] = 1
                st.append((ni, nj))

for i in range(H):
    for j in range(W):
        if reachable1[i][j] and reachable2[i][j]:
            print(0)
            exit()

for i in range(H):
    for j in range(W):
        if (i < 3 and j < 3) or (i >= H-3 and j >= W-3):
            continue
        r1 = r2 = 0
        if i >= H-3 or j < 3:
            r1 = 1
        if i < 3 or j >= W-3:
            r2 = 1
        for ni in range(i-3, i+4):
            for nj in range(j-3, j+4):
                if abs(i-ni)+abs(j-nj) <= 5 and 0 <= ni < H and 0 <= nj < W:
                    r1 |= reachable1[ni][nj]
                    r2 |= reachable2[ni][nj]
        if r1 and r2:
            print(1)
            exit()

print(2)