using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using static System.Math;
using static System.Array;
using static AtCoder.Tool;
namespace AtCoder
{
    class AC
    {
        const int MOD = 1000000007;
        const int INF = int.MaxValue / 2;
        const long SINF = long.MaxValue / 2;
        const double EPS = 1e-8;
        static readonly int[] dx = { 0, 1, 0, -1 };
        static readonly int[] dy = { 1, 0, -1, 0 };
        static List<List<int>> G = new List<List<int>>();
        //static List<List<Edge>>G = new List<List<Edge>>();
        //static List<Edge> E = new List<Edge>();

        static void Main(string[] args)
        {
            //var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            //Console.SetOut(sw);
            var cin = new Scanner();

            var input = cin.ReadSplit();
            int H = input[0];
            int W = input[1];
            var map = new char[H + 1][];
            for(var i = 0; i <= H; i++)
            {
                map[i] = new char[W + 1];
                if (i == H)
                {
                    for (var j = 0; j <= W; j++) map[i][j] = '.';
                }
                else
                {
                    var p = Console.ReadLine();
                    for(var j = 0; j <= W; j++)
                    {
                        map[i][j] = j == W ? '.' : p[j];
                    }
                }
            }
            var ch = new bool[H + 1][];
            for(var i = 0; i <= H; i++)
            {
                ch[i] = new bool[W + 1];
                Initialize(ref ch[i], false);
            }
            Func<int, int, int> dfs = null;
            dfs = (i, j) =>
            {
                ch[i][j] = true;
                if (map[i + 1][j] == '#' && !ch[i + 1][j]) { dfs(i + 1, j); }
                else if (map[i][j + 1] == '#' && !ch[i][j + 1]) { dfs(i, j + 1); }
                return 0;
            };
            dfs(0, 0);
            for(var i = 0; i < H; i++)
            {
                for(var j = 0; j < W; j++)
                {
                    if (map[i][j] == '#'&&!ch[i][j]) { Console.WriteLine("Impossible");return; }
                }
            }
            Console.WriteLine("Possible");

            //Console.Out.Flush();
        }
        struct Edge
        {
            public int from;

            public int to;
            public long dist;
            public Edge(int t, long c)
            {
                from = -1;
                to = t;
                dist = c;
            }
            public Edge(int f, int t, long c)
            {
                from = f;
                to = t;
                dist = c;
            }

        }
    }
    public class Scanner
    {
        public int[] ReadSplit()
        {
            return ConvertAll(Console.ReadLine().Split(), int.Parse);
        }
        public long[] ReadSplitL()
        {
            return ConvertAll(Console.ReadLine().Split(), long.Parse);
        }
        public double[] ReadSplitD()
        {
            return ConvertAll(Console.ReadLine().Split(), double.Parse);
        }
    }
    public static class Tool
    {
        static public void Initialize<T>(ref T[] array, T initialvalue)
        {
            for (var i = 0; i < array.Length; i++)
            {
                array[i] = initialvalue;
            }
        }
        static public void Swap<T>(ref T a, ref T b)
        {
            T keep = a;
            a = b;
            b = keep;
        }

        static public void Display<T>(T[,] array2d, int n, int m)
        {
            for (var i = 0; i < n; i++)
            {
                for (var j = 0; j < m; j++)
                {
                    Console.Write($"{array2d[i, j]} ");
                }
                Console.WriteLine();
            }
        }

        static long LPow(int a, int b)
        {
            return (long)Pow(a, b);
        }
    }
}


Measured memory_bytes: 13268