using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using Enu = System.Linq.Enumerable;

class Program
{
    static readonly int INF = (int)1e9;
    static readonly int[] DR = { 0, 0, -1, 1 };
    static readonly int[] DC = { -1, 1, 0, 0 };

    void Solve()
    {
        int W = reader.Int(), H = reader.Int();
        var grid = reader.StringArray(H);
        int[,] dist = new int[H * W, H * W];
        Func<int, int, int> Id = (r, c) => r * W + c;
        Func<int, int, bool> IsInside = (r, c) => r >= 0 && r < H && c >= 0 && c < W;

        for (int a = 0; a < H * W; a++)
            for (int b = a + 1; b < H * W; b++)
                dist[a, b] = dist[b, a] = INF;
        for (int r = 0; r < H; r++)
            for (int c = 0; c < W; c++)
                for (int d = 0; d < DR.Length; d++)
                {
                    int nr = r + DR[d], nc = c + DC[d];
                    if (IsInside(nr, nc))
                        dist[Id(r, c), Id(nr, nc)] = (grid[nr][nc] == '.') ? 0 : 1;
                }
        for (int c = 0; c < H * W; c++)
            for (int a = 0; a < H * W; a++)
                for (int b = 0; b < H * W; b++)
                    dist[a, b] = Math.Min(dist[a, b], dist[a, c] + dist[c, b]);
        int ans = INF;
        for (int r = 0; r < H; r++)
            for (int c = 0; c < W; c++)
                for (int nr = 0; nr < H; nr++)
                    for (int nc = 0; nc < W; nc++)
                        if ((r != nr || c != nc) && grid[r][c] == '.' && grid[nr][nc] == '.')
                        {
                            int d = dist[Id(r, c), Id(nr, nc)];
                            if (d > 0) ans = Math.Min(ans, d);
                        }

        Console.WriteLine(ans);
    }





    Reader reader = new Reader(Console.In);
    static void Main() { new Program().Solve(); }
}

class Reader
{
    private readonly TextReader reader;
    private readonly char[] separator = { ' ' };
    private readonly StringSplitOptions removeOp = StringSplitOptions.RemoveEmptyEntries;
    private string[] A = new string[0];
    private int i;

    public Reader(TextReader r) { reader = r; }
    public Reader(string file) { reader = new StreamReader(file); }
    public bool HasNext() { return Enqueue(); }
    public string String() { return Dequeue(); }
    public int Int() { return int.Parse(Dequeue()); }
    public long Long() { return long.Parse(Dequeue()); }
    public double Double() { return double.Parse(Dequeue()); }
    public int[] IntLine() { var s = Line(); return s == "" ? new int[0] : Array.ConvertAll(Split(s), int.Parse); }
    public int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public int[][] IntGrid(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public string Line() { return reader.ReadLine().Trim(); }
    private string[] Split(string s) { return s.Split(separator, removeOp); }
    private bool Enqueue()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return Enqueue();
        A = Split(line);
        i = 0;
        return true;
    }
    private string Dequeue() { Enqueue(); return A[i++]; }
}