#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>
#include <queue>

using namespace std;

const int dx[4] = {0, 1, 0, -1};
const int dy[4] = {1, 0, -1, 0};
int w, h;

bool is_inside(int x, int y) {
	return (0 <= x && x <= w && 0 <= y && y <= h);
}

int main() {

	cin >> w >> h;
	vector<string> board(h, "");
	for (int i = 0; i < h; i++) {
		cin >> board[i];
	}

	int x, y;
	for (int i = 0; i < h; i++) {
		for (int j = 0; j < w; j++) {
			if (board[i][j] == '.') {
				x = j;
				y = i;
				break;
			}
		}
	}
	queue<int> que_start;
	queue< pair<int, int> > que_wall;

	que_start.push(x * 100 + y);
	que_wall.push(make_pair(x * 100 + y, 0));
	board[y][x] = 'S';

	int nx, ny;
	while (!que_start.empty()) {
		auto pos = que_start.front();
		que_start.pop();

		for (int i = 0; i < 4; i++) {
			nx = pos / 100 + dx[i];
			ny = pos % 100 + dy[i];
			if (is_inside(nx, ny) && board[ny][nx] == '.') {
				board[ny][nx] = 'S';
				que_start.push(nx * 100 + ny);
				que_wall.push(make_pair(nx * 100 + ny, 0));
			}
		}
	}

	int ans = -1;
	while (!que_wall.empty() && ans == -1) {
		auto pos = que_wall.front();
		que_wall.pop();

		for (int i = 0; i < 4; i++) {
			nx = pos.first / 100 + dx[i];
			ny = pos.first % 100 + dy[i];
			if (is_inside(nx, ny)) {
				if (board[ny][nx] == '.') {
					ans = pos.second;
					break;
				} else if (board[ny][nx] == '#') {
					board[ny][nx] = '+';
					que_wall.push(make_pair(nx * 100 + ny, pos.second + 1));
				}
			}
		}
	}

	cout << ans << endl;
	return 0;
}