import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int w = sc.nextInt();
		int h = sc.nextInt();
		char[][] field = new char[h][];
		for (int i = 0; i < h; i++) {
		    field[i] = sc.next().toCharArray();
		}
		ArrayDeque<Integer> deq = new ArrayDeque<>();
		for (int i = 1; i < h - 1 && deq.size() == 0; i++) {
		    for (int j = 1; j < w - 1 && deq.size() == 0; j++) {
		        if (field[i][j] == '.') {
		            deq.add(i * w + j);
		        }
		    }
		}
		HashSet<Integer> holeA = new HashSet<>();
		while (deq.size() > 0) {
		    int x = deq.poll();
		    if (field[x / w][x % w] == '.' && !holeA.contains(x)) {
		        holeA.add(x);
		        deq.add(x - 1);
		        deq.add(x + 1);
		        deq.add(x - w);
		        deq.add(x + w);
		    }
		}
		int min = Integer.MAX_VALUE;
		for (int i = 1; i < h - 1; i++) {
		    for (int j = 1; j < w - 1; j++) {
		        if (field[i][j] == '.' && !holeA.contains(i * w + j)) {
		            for (int x : holeA) {
		                min = Math.min(min, Math.abs(x / w - i) + Math.abs(x % w - j));
		            }
		        }
		    }
		}
		System.out.println(min - 1);
   }
}