import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Main {

    static BufferedReader in;
    static PrintWriter out;
    static StringTokenizer tok;

    void solve() throws IOException {
        int h = ni();
        int w = ni();

        String[] a = nsa(h);

        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                if (i > 0 && j > 0) {
                    if (a[i].charAt(j) == '#' && (a[i - 1].charAt(j) == '#' && a[i].charAt(j - 1) == '#' || a[i - 1].charAt(j) == '.' && a[i].charAt(j - 1) == '.')) {
                        out.println("Impossible");
                        return;
                    }
                } else if (i > 0) {
                    if (a[i].charAt(j) == '#' && a[i - 1].charAt(j) == '.' ) {
                        out.println("Impossible");
                        return;
                    }
                } else if (j > 0) {
                    if (a[i].charAt(j) == '#' && a[i].charAt(j - 1) == '.' ) {
                        out.println("Impossible");
                        return;
                    }
                }

                if (i < h - 1 && j < w - 1) {
                    if (a[i].charAt(j) == '#' && (a[i + 1].charAt(j) == '#' && a[i].charAt(j + 1) == '#' || a[i + 1].charAt(j) == '.' && a[i].charAt(j + 1) == '.')) {
                        out.println("Impossible");
                        return;
                    }
                } else if (i < h - 1) {
                    if (a[i].charAt(j) == '#' && a[i + 1].charAt(j) == '.' ) {
                        out.println("Impossible");
                        return;
                    }
                } else if (j < w - 1) {
                    if (a[i].charAt(j) == '#' && a[i].charAt(j + 1) == '.' ) {
                        out.println("Impossible");
                        return;
                    }
                }
            }
        }

        out.println("Possible");
    }

    String ns() throws IOException {
        while (!tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.readLine(), " ");
        }
        return tok.nextToken();
    }

    int ni() throws IOException {
        return Integer.parseInt(ns());
    }

    long nl() throws IOException {
        return Long.parseLong(ns());
    }

    double nd() throws IOException {
        return Double.parseDouble(ns());
    }

    String[] nsa(int n) throws IOException {
        String[] res = new String[n];
        for (int i = 0; i < n; i++) {
            res[i] = ns();
        }
        return res;
    }

    int[] nia(int n) throws IOException {
        int[] res = new int[n];
        for (int i = 0; i < n; i++) {
            res[i] = ni();
        }
        return res;
    }

    long[] nla(int n) throws IOException {
        long[] res = new long[n];
        for (int i = 0; i < n; i++) {
            res[i] = nl();
        }
        return res;
    }

    public static void main(String[] args) throws IOException {
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
        tok = new StringTokenizer("");
        Main main = new Main();
        main.solve();
        out.close();
    }
}

Measured memory_bytes: 8268