#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;
using P = pair<int, int>;
constexpr ld EPS = 1e-12;
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr int MOD = 1e9 + 7;

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

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int W, H;
    cin >> W >> H;
    vector<string> s(H);
    int sx, sy;
    for (int i = 0; i < H; i++)
    {
        cin >> s[i];
        for (int j = 0; j < W; j++)
        {
            if (s[i][j] == '.')
            {
                sx = i;
                sy = j;
            }
        }
    }
    vector<vector<int>> dis(H, vector<int>(W, INF));
    queue<P> q;
    q.push(P(sx, sy));
    dis[sx][sy] = 0;
    while (!q.empty())
    {
        P p = q.front();
        q.pop();
        int x = p.first, y = p.second;
        s[x][y] = '#';
        for (int i = 0; i < 4; i++)
        {
            int nx = x + dx[i], ny = y + dy[i];
            if (nx < 0 || H <= nx || ny < 0 || W <= ny)
                continue;
            if (dis[nx][ny] != INF)
                continue;
            if (s[nx][ny] != '.')
                continue;
            dis[nx][ny] = 0;
            q.push(P(nx, ny));
        }
    }
    for (int i = 0; i < H; i++)
        for (int j = 0; j < W; j++)
            if (dis[i][j] == 0)
                q.push(P(i, j));
    while (!q.empty())
    {
        P p = q.front();
        q.pop();
        int x = p.first, y = p.second;
        for (int i = 0; i < 4; i++)
        {
            int nx = x + dx[i], ny = y + dy[i];
            if (nx < 0 || H <= nx || ny < 0 || W <= ny)
                continue;
            if (dis[nx][ny] != INF)
                continue;
            if (s[nx][ny] == '.')
            {
                cout << dis[x][y] << endl;
                return 0;
            }
            dis[nx][ny] = dis[x][y] + 1;
            q.push(P(nx, ny));
        }
    }
}