import java.io.BufferedWriter;


import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Writer;
import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Random;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeSet;
public class Main {
	
	public interface SpaceCharFilter {
        public boolean isSpaceChar(int ch);
        }
    class InputReader {


        private InputStream stream;

        private byte[] buf = new byte[1024];

        private int curChar;

        private int numChars;

        private SpaceCharFilter filter;
        

        public InputReader(InputStream stream) {

            this.stream = stream;

        }


        public int read() {

            if (numChars == -1)

                throw new InputMismatchException();

            if (curChar >= numChars) {

                curChar = 0;

                try {

                    numChars = stream.read(buf);

                } catch (IOException e) {

                    throw new InputMismatchException();

                }

                if (numChars <= 0)

                    return -1;

            }

            return buf[curChar++];

        }


        public int readInt() {

            int c = read();

            while (isSpaceChar(c))

                c = read();

            int sgn = 1;

            if (c == '-') {

                sgn = -1;

                c = read();

            }

            int res = 0;

            do {

                if (c < '0' || c > '9')

                    throw new InputMismatchException();

                res *= 10;

                res += c - '0';

                c = read();

            } while (!isSpaceChar(c));

            return res * sgn;

        }
        public long readLong() {

            int c = read();

            while (isSpaceChar(c))

                c = read();

            int sgn = 1;

            if (c == '-') {

                sgn = -1;

                c = read();

            }

            long res = 0;

            do {

                if (c < '0' || c > '9')

                    throw new InputMismatchException();

                res *= 10;

                res += c - '0';

                c = read();

            } while (!isSpaceChar(c));

            return res * sgn;

        }

        public String readString() {

            int c = read();

            while (isSpaceChar(c))

                c = read();

            StringBuilder res = new StringBuilder();

            do {

                res.appendCodePoint(c);

                c = read();

            } while (!isSpaceChar(c));

            return res.toString();

        }


        public boolean isSpaceChar(int c) {

            if (filter != null)

                return filter.isSpaceChar(c);

            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;

        }


        public String next() {

            return readString();

        }



    }


class OutputWriter {

        private final PrintWriter writer;


        public OutputWriter(OutputStream outputStream) {

            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));

        }


        public OutputWriter(Writer writer) {

            this.writer = new PrintWriter(writer);

        }


        public void print(Object...objects) {

            for (int i = 0; i < objects.length; i++) {

                if (i != 0)

                    writer.print(' ');

                writer.print(objects[i]);

            }

        }


        public void printLine(Object...objects) {

            print(objects);

            writer.println();

        }


        public void close() {

            writer.close();

        }


        public void flush() {

            writer.flush();

        }


        }

    /**
     * @param args
     */

    InputReader in= new InputReader(System.in);
    OutputWriter out = new OutputWriter(System.out);
        StringTokenizer tok;
      
        public static void main(String[] args) throws IOException
        {
           new Main().run();
        }
        void run() throws IOException
        {
            
           solve();
           out.flush();
           tok=null;
        }
      

void  solve() throws IOException{
	int H=in.readInt();
	int W=in.readInt();
	int last_rock=0;
	int last_i=0;
	boolean sol=true;
	for (int i=0;i<H;++i){
		String s=in.readString();
		if (i==0 && s.charAt(0)!='#') {sol=false; break;}
		if (i==H-1 && s.charAt(W-1)!='#'){ sol=false; break;}
		for (int j=0;j<W;++j){
			if (s.charAt(j)=='#'){
				if (j<last_rock){
					sol=false;
					break;
				}else {
					if (j-last_rock>1){
						sol=false;
					}else if (i-last_i>1){
						sol=false;
					}else{
						last_rock=j;
						last_i=i;
					}
				}
					
			} if (!sol) break;
		}
	}
	if (sol) out.printLine("Possible");
	else out.printLine("Impossible");
}        
}

Measured memory_bytes: 8404