JaeHyeonKim19

import java.io.*;
import java.util.*;

public class Main {
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int m = Integer.parseInt(st.nextToken());
		int n = Integer.parseInt(st.nextToken());
		int h = Integer.parseInt(st.nextToken());
		int [][][] tomatoes = new int[n][m][h];
		int [][][] curTomatoes = new int[n][m][h];
		int answer = 0;
		Queue<int []> q = new LinkedList();
		for(int i = 0; i < h; i++) {
			for(int j = 0; j < n; j++) {
				st = new StringTokenizer(br.readLine());
				for(int k = 0; k < m; k++) {
					int curToken = Integer.parseInt(st.nextToken());
					tomatoes[j][k][i] = curToken;
					curTomatoes[j][k][i] = curToken;
				}
			}
		}
		boolean isImpossible = false;
		for(int i = 0; i < h; i++) {
			for(int j = 0; j < n; j++) {
				for(int k = 0; k < m; k++) {
					if(tomatoes[j][k][i] == 1) {
						if(j-1>=0 && tomatoes[j-1][k][i] == 0) {
							curTomatoes[j-1][k][i] = tomatoes[j][k][i]+1;
							int [] coordinate = {j-1, k, i};
							q.offer(coordinate);
						}
						if(k-1>=0 && tomatoes[j][k-1][i] == 0) {
							curTomatoes[j][k-1][i] = tomatoes[j][k][i]+1;
							int [] coordinate = {j, k-1, i};
							q.offer(coordinate);
						}
						if(i-1>=0 && tomatoes[j][k][i-1] == 0) {
							curTomatoes[j][k][i-1] = tomatoes[j][k][i]+1;
							int [] coordinate = {j, k, i-1};
							q.offer(coordinate);
						}
						if(j+1<n && tomatoes[j+1][k][i] == 0) {
							curTomatoes[j+1][k][i] = tomatoes[j][k][i]+1;
							int [] coordinate = {j+1, k, i};
							q.offer(coordinate);
						}
						if(k+1<m && tomatoes[j][k+1][i] == 0) {
							curTomatoes[j][k+1][i] = tomatoes[j][k][i]+1;
							int [] coordinate = {j, k+1, i};
							q.offer(coordinate);
						}
						if(i+1<h && tomatoes[j][k][i+1] == 0) {
							curTomatoes[j][k][i+1] = tomatoes[j][k][i]+1;
							int [] coordinate = {j, k, i+1};
							q.offer(coordinate);
						}
					}else if(tomatoes[j][k][i] == 0) {
						isImpossible = true;
					}
				}
			}
		}
		if(q.isEmpty() && !isImpossible) {
			System.out.print(0);
			return;
		}else if(q.isEmpty() && isImpossible) {
			System.out.print(-1);
			return;
		}
		while(!q.isEmpty()) {
			int [] curCoordinate = q.poll();
			int j = curCoordinate[0];
			int k = curCoordinate[1];
			int i = curCoordinate[2];
			if(j-1>=0 && curTomatoes[j-1][k][i] == 0) {
				curTomatoes[j-1][k][i] = curTomatoes[j][k][i]+1;
				answer = curTomatoes[j][k][i];
				int [] coordinate = {j-1, k, i};
				q.offer(coordinate);
			}
			if(k-1>=0 && curTomatoes[j][k-1][i] == 0) {
				curTomatoes[j][k-1][i] = curTomatoes[j][k][i]+1;
				answer = curTomatoes[j][k][i];
				int [] coordinate = {j, k-1, i};
				q.offer(coordinate);
			}
			if(i-1>=0 && curTomatoes[j][k][i-1] == 0) {
				curTomatoes[j][k][i-1] = curTomatoes[j][k][i]+1;
				answer = curTomatoes[j][k][i];
				int [] coordinate = {j, k, i-1};
				q.offer(coordinate);
			}
			if(j+1<n && curTomatoes[j+1][k][i] == 0) {
				curTomatoes[j+1][k][i] = curTomatoes[j][k][i]+1;
				answer = curTomatoes[j][k][i];
				int [] coordinate = {j+1, k, i};
				q.offer(coordinate);
			}
			if(k+1<m && curTomatoes[j][k+1][i] == 0) {
				curTomatoes[j][k+1][i] = curTomatoes[j][k][i]+1;
				answer = curTomatoes[j][k][i];
				int [] coordinate = {j, k+1, i};
				q.offer(coordinate);
			}
			if(i+1<h && curTomatoes[j][k][i+1] == 0) {
				curTomatoes[j][k][i+1] = curTomatoes[j][k][i]+1;
				answer = curTomatoes[j][k][i];
				int [] coordinate = {j, k, i+1};
				q.offer(coordinate);
			}
			if(q.isEmpty()) {
				for(int x = 0; x < h; x++) {
					for(int y = 0; y < n; y++) {
						for(int z = 0; z < m; z++) {
							if(curTomatoes[y][z][x] == 0) {
								System.out.print(-1);
								return;
							}
						}
					}
				}
				System.out.print(answer);
			}
		}
	}
}