board = [[0]*M for i in range(N)]

day = 1

count = N*M

for i in range(0, 2*L, 2):

x = battalion[i] - 1

y = battalion[i+1] - 1

if board[x][y] == 0:

board[x][y] = 1

count -= 1

while count != 0:

new_board = [[board[i][j] for j in range(M)] for i in range(N)]

for i in range(N):

for j in range(M):

if board[i][j] == 1:

for x, y in (i-1, j), (i, j-1), (i, j+1), (i+1, j):

if 0 <= x < N and 0 <= y < M and new_board[x][y] == 0:

new_board[x][y] = 1

count -= 1

board = new_board

day += 1