#7569번 토마토 #백준 #BFS #삼차원 배열

#문제 링크

https://www.acmicpc.net/problem/7569

7569번: 토마토

#code

#7569 토마토 BFS활용

import sys

from collections import deque

input = sys.stdin.readline

m, n, h = map(int, input().split())

data = []

def bfs(data, data_1):

    queue = deque(data_1)

    for d in queue:

        v[d[0]][d[1]][d[2]] = 1

    count = 0

    while queue:

        size = len(queue)

        for _ in range(size):

            cx, cy, cz = queue.popleft()

            for i, j, k in zip(x, y, z):

                dx = cx + i

                dy = cy + j

                dz = cz + k

                if 0 <= dx < h and 0 <= dy < n and 0 <= dz < m and v[dx][dy][dz] == -1 and data[dx][dy][dz] != '-1' and data[dx][dy][dz] != '1':

                    queue.append((dx, dy, dz))

                    v[dx][dy][dz] = 1

       

        count += 1

    for i in range(h):

        for j in range(n):

            for k in range(m):

                if v[i][j][k] == -1 and data[i][j][k] != '-1':

                    return -1

    return max(0, count - 1)

x = [1, -1, 0, 0, 0, 0]

y = [0, 0, 1, -1, 0, 0]

z = [0, 0, 0, 0, 1, -1]

for i in range(h):

    data_xy = []

    for j in range(n):

        data_xy.append(input().strip().split())

    data.append(data_xy)

data_1 = []

v = [[[-1]*m for _ in range(n)] for _ in range(h)]

for i in range(h):

    for j in range(n):

        for k in range(m):

            if data[i][j][k] == '1':

                data_1.append((i, j, k))

            elif data[i][j][k] == '-1':

                v[i][j][k] = 1  # 익지 못하는 토마토로 표시

print(bfs(data, data_1))