def binary_matrix(A):

row, col = len(A), len(A[0])

dp = [[0 for j in range(col)] for i in range(row)]

for i in range(row):

dp[i][0] = A[i][0]

for j in range(col):

dp[0][j] = A[0][j]

for i in range(1, row):

for j in range(1, col):

if A[i][j] == 0:

dp[i][j] = 0

else:

dp[i][j] = 1 + min(dp[i - 1][j], dp[i][j - 1], dp[i - 1][j - 1])

max_ele = dp[0][0]

max_i, max_j = 0, 0

for i in range(row):

for j in range(col):

if max_ele < dp[i][j]:

max_ele = dp[i][j]

max_i, max_j = i, j

k = max_ele

return k

M = [[0, 1, 1, 0, 1],

[1, 1, 0, 1, 0],

[0, 1, 1, 1, 0],

[1, 1, 1, 1, 0],

[1, 1, 1, 1, 1],

[0, 0, 0, 0, 0]]

print(binary_matrix(M))