data = open('input', 'r').readlines()
data = [list(x.strip()) for x in data]


def neighbors(mat, x, y):
    height = len(mat)
    width = len(mat[0])
    for i in range(3):
        for j in range(3):
            dx = i - 1
            dy = j - 1
            if dx == 0 and dy == 0:
                continue
            if x + dx < 0 or y + dy < 0:
                continue
            if x + dx >= height or y + dy >= width:
                continue
            yield data[x + dx][y+dy]


def serialize(mat):
    return '\n'.join([''.join(line) for line in mat])


def apply(mat):
    newData = []
    for x, _ in enumerate(mat):
        line = []
        for y, _ in enumerate(mat[x]):
            neigh = list(neighbors(mat, x, y))
            if mat[x][y] == 'L' and '#' not in neigh:
                line.append('#')
            elif mat[x][y] == '#' and neigh.count('#') >= 4:
                line.append('L')
            else:
                line.append(mat[x][y])
        newData.append(line)
    return newData


prev = ''

while serialize(data) != prev:
    prev = serialize(data)
    data = apply(data)


# print(serialize(data))
print(prev.count('#'))