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

public class AtCoderA
{
    static void Main()
    {
        var sc = new Scanner();

        int h = sc.NextInt();
        int w = sc.NextInt();
        bool[,] map = new bool[h, w];
        for (int i = 0; i < h; i++)
        {
            string s = sc.Next();
            for (int j = 0; j < w; j++)
            {
                map[i, j] = s[j] == '#';
            }
        }

        int currentH = 0;
        int currentW = 0;

        bool ok = true;

        while (true)
        {
            int[] hs = new int[] { -1, 1, 0, 0 };
            int[] ws = new int[] { 0, 0, -1, 1 };
            bool[] dirction = new bool[4];
            for (int i = 0; i < 4; i++)
            {
                int newH = currentH + hs[i];
                int newW = currentW + ws[i];
                if (newH < 0 || newH >= h || newW < 0 || newW >= w)
                {
                    continue;
                }
                if (map[newH, newW])
                {
                    dirction[i] = true;
                }
            }

            if (currentW == w - 1 && currentH == h - 1)
            {
                if (dirction.Where(b => b).Count() >= 2)
                {
                    ok = false;
                    break;
                }
                break;
            }

            if (dirction.Where(b => b).Count() >= 3)
            {
                ok = false;
                break;
            }
            if (dirction[1] && dirction[3])
            {
                ok = false;
                break;
            }
            if (!dirction[1] && !dirction[3])
            {
                ok = false;
                break;
            }

            if (dirction[3])
            {
                currentW++;
            }
            if (dirction[1])
            {
                currentH++;
            }
        }

        string answer = ok ? "Possible" : "Impossible";

        Console.WriteLine(answer);
    }

    class Scanner
    {
        private string[] _line;
        private int _index;
        private const char Separator = ' ';

        public Scanner()
        {
            _line = new string[0];
            _index = 0;
        }

        public string Next()
        {
            while (_index >= _line.Length)
            {
                _line = Console.ReadLine().Split(Separator);
                _index = 0;
            }

            return _line[_index++];
        }

        public int NextInt() => int.Parse(Next());
        public long NextLong() => long.Parse(Next());
        public double NextDouble() => double.Parse(Next());
        public decimal NextDecimal() => decimal.Parse(Next());
        public char NextChar() => Next()[0];
        public char[] NextCharArray() => Next().ToCharArray();

        public string[] Array()
        {
            _line = Console.ReadLine().Split(Separator);
            _index = _line.Length;
            return _line;
        }

        public int[] IntArray() => Array().Select(int.Parse).ToArray();
        public long[] LongArray() => Array().Select(long.Parse).ToArray();
        public double[] DoubleArray() => Array().Select(double.Parse).ToArray();
        public decimal[] DecimalArray() => Array().Select(decimal.Parse).ToArray();
    }
}


Measured memory_bytes: 13396