Kutep

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace _7
{

    class Program
    {
        static int CortSize = 52;
        static bool[,] Cort = new bool[CortSize, CortSize];

        static bool IsSolidWithout(int x, int y)
        {
            Cort[x, y] = false;
            bool[,] ConnectionMap = new bool[CortSize, CortSize];
            bool IsSolid = false;

            int WaysBefore = 0;
            WaysBefore += Cort[x + 1, y] ? 1 : 0;
            WaysBefore += Cort[x - 1, y] ? 1 : 0;
            WaysBefore += Cort[x, y + 1] ? 1 : 0;
            WaysBefore += Cort[x, y - 1] ? 1 : 0;

            if (WaysBefore > 1)
            {
                if (Cort[x + 1, y]) setConnection(ref ConnectionMap, x + 1, y);
                else if (Cort[x - 1, y]) setConnection(ref ConnectionMap, x - 1, y);
                else setConnection(ref ConnectionMap, x, y + 1);


                int WaysAfter = 0;
                WaysAfter += ConnectionMap[x + 1, y] ? 1 : 0;
                WaysAfter += ConnectionMap[x - 1, y] ? 1 : 0;
                WaysAfter += ConnectionMap[x, y + 1] ? 1 : 0;
                WaysAfter += ConnectionMap[x, y - 1] ? 1 : 0;

                IsSolid = WaysAfter != WaysBefore;
            }

            Cort[x, y] = true;

            return IsSolid;
        }

        static void setConnection(ref bool[,] Map, int x, int y)
        {
            Map[x, y] = true;
            if (Cort[x + 1, y] && !Map[x + 1, y]) setConnection(ref Map, x + 1, y);
            if (Cort[x - 1, y] && !Map[x - 1, y]) setConnection(ref Map, x - 1, y);
            if (Cort[x, y + 1] && !Map[x, y + 1]) setConnection(ref Map, x, y + 1);
            if (Cort[x, y - 1] && !Map[x, y - 1]) setConnection(ref Map, x, y - 1);
        }

        static void Main(string[] args)
        {
            int result = 0;

            StreamReader SR = new StreamReader("Input.txt");
            string[] buf = SR.ReadLine().Split(' ');
            int n = int.Parse(buf[0]), m = int.Parse(buf[1]);

            for (int i = 1; i <= n; i++)
            {
                string line = SR.ReadLine();
                for (int j = 1; j <= m; j++)
                {
                    if (line[j - 1] == '#')
                    {
                        Cort[i, j] = true;
                        result++;
                    }
                }
            }
            SR.Close();

            if (result > 2)
            {
                for (int i = 1; i <= n && result != 1; i++)
                {
                    for (int j = 1; j <= m && result != 1; j++)
                    {
                        result = Cort[i, j] && IsSolidWithout(i, j) ? 1 : 2;
                    }
                }
            }
            else
            {
                result = -1;
            }

            StreamWriter SW = new StreamWriter("Output.txt");
            SW.Write(result);
            SW.Close();
        }
    }
}