#!/usr/bin/python3

from pprint import pprint

def read_area():
    area = []
    with open("input") as fh:
        for ln in fh:
            area.append(list(ln.strip()))
    return area

def neighbours(area, i, j):

    count = 0
    for i1 in (-1, 0, 1):
        if i + i1 < 0:
            continue
        if i + i1 >= len(area):
            continue
        for j1 in (-1, 0, 1):
            if i1 == j1 == 0:
                continue
            if j + j1 < 0:
                continue
            if j + j1 >= len(area[i + i1]):
                continue
            count += area[i + i1][j + j1] == "#"
    return count

def new_occ(area, i, j):
    if area[i][j] == ",":
        return "."
    if area[i][j] == "L" and neighbours(area, i, j) == 0:
        return "#"
    if area[i][j] == "#" and neighbours(area, i, j) >= 4:
        return "L"
    return area[i][j]

def next_tick(area):
    new_area = []
    for i in range(len(area)):
        new_row = []
        for j in range(len(area[i])):
            new_row.append(new_occ(area, i, j))
        new_area.append(new_row)
    return new_area

def count_occupied(area):
    sum = 0
    for row in area:
        for seat in row:
            sum += seat == "#"
    return sum

area = read_area()
while True:
    new_area = next_tick(area)
    if new_area == area:
        break
    area = new_area
print(count_occupied(area))