import java.io.*;
import java.util.*;

class Main {
    static char[][] grid;
    static int tx, ty,m, n;
    static int[] cnts;
    
    public static void main(String[] args) throws IOException {
        Scan sc = new Scan();
        m = sc.scanInt();
        n = sc.scanInt();
        grid = new char[m][n];
        cnts = new int[m];
        tx = m-1;
        ty = n-1;
        for(int i= 0; i < m; ++i){
            int cnt = 0;
            for(int j =0; j < n; ++j){
                grid[i][j] = sc.scanChar();
                if(grid[i][j] == '#')
                    ++cnt;
            }
            cnts[i] = cnt;
        }
        
        int start = 0;
        int i = 0;
        boolean good = true;
        for(; i < m; ++i){
            int orig = start;
            while(start < n && grid[i][start]=='#')
                ++start;
            if(start-orig!=cnts[i]){
                good = false;
                break;
            }
            --start;
        }
        if(!good)
            System.out.println("Impossible");
        else
            System.out.println("Possible");
        
    }
}

class Scan
{
    private byte[] buf=new byte[1024];
    private int index;
    private InputStream in;
    private int total;
    public Scan()
    {
        in=System.in;
    }
    public int scan()throws IOException
    {
        if(total<0)
        throw new InputMismatchException();
        if(index>=total)
        {
            index=0;
            total=in.read(buf);
            if(total<=0)
            return -1;
        }
        return buf[index++];
    }
    public char scanChar() throws IOException {
        int n = scan();
        while(isWhiteSpace(n))
            n=scan();
        return (char)n;
    }
    public int scanInt()throws IOException
    {
        int integer=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n))
        {
            if(n>='0'&&n<='9')
            {
                integer*=10;
                integer+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        return neg*integer;
    }
    public long scanLong() throws IOException {
        long integer=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n))
        {
            if(n>='0'&&n<='9')
            {
                integer*=10;
                integer+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        return neg*integer;
    }
    public double scanDouble()throws IOException
    {
        double doub=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n)&&n!='.')
        {
            if(n>='0'&&n<='9')
            {
                doub*=10;
                doub+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        if(n=='.')
        {
            n=scan();
            double temp=1;
            while(!isWhiteSpace(n))
            {
                if(n>='0'&&n<='9')
                {
                    temp/=10;
                    doub+=(n-'0')*temp;
                    n=scan();
                }
                else throw new InputMismatchException();
            }
        }
        return doub*neg;
    }
    public String scanString()throws IOException
    {
        StringBuilder sb=new StringBuilder();
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        while(!isWhiteSpace(n))
        {
            sb.append((char)n);
            n=scan();
        }
        return sb.toString();
    }
    public boolean isWhiteSpace(int n)
    {
        if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
        return true;
        return false;
    }
}


Measured memory_bytes: 21204