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

public class Main{

  public static void main(String[] args) {
    InputReader in = new InputReader(System.in);
    PrintWriter w = new PrintWriter(System.out);

    int r = in.nextInt();
    int c = in.nextInt();

    char s[][] = new char[r][c];
    for (int i = 0; i < r; i++)
      s[i] = in.readString().toCharArray();

    String p = "Possible";
    String ip = "Impossible";

    int cnt = 0;
    for (char d[] : s)
      for (char y : d)
        if (y == '#')
          cnt++;
    
    System.out.println(cnt == (r - 1) + (c - 1) + 1 ? p : ip);
    
    /*
    if (s[0][0] == '.' || s[r - 1][c - 1] == '.') {
      System.out.println(ip);
      return;
    }

    boolean d[][] = new boolean[r][c];
    
    int i = 0, j = 0;

    while (true) {
      if (i + 1 < r && s[i + 1][j] == '#') {
        if (j + 1 < c && s[i][j + 1] == '#') {
          System.out.println(ip);
          return;
        }
        i++;
        continue;
      }
      if (j + 1 < c && s[i][j + 1] == '#') {
        if (i + 1 < r && s[i + 1][j] == '#') {
          System.out.println(ip);
          return;
        }
        j++;
        continue;
      }
      break;
    }
    
    if (i != r - 1 || j != c - 1) 
      System.out.println(ip);
    else
      System.out.println(p);
    w.close();*/
  }

  static class InputReader {

    private final InputStream stream;
    private final byte[] buf = new byte[8192];
    private int curChar, snumChars;
    private SpaceCharFilter filter;

    public InputReader(InputStream stream) {
      this.stream = stream;
    }

    public int snext() {
      if (snumChars == -1)
        throw new InputMismatchException();
      if (curChar >= snumChars) {
        curChar = 0;
        try {
          snumChars = stream.read(buf);
        } catch (IOException e) {
          throw new InputMismatchException();
        }
        if (snumChars <= 0)
          return -1;
      }
      return buf[curChar++];
    }

    public int nextInt() {
      int c = snext();
      while (isSpaceChar(c)) {
        c = snext();
      }
      int sgn = 1;
      if (c == '-') {
        sgn = -1;
        c = snext();
      }
      int res = 0;
      do {
        if (c < '0' || c > '9')
          throw new InputMismatchException();
        res *= 10;
        res += c - '0';
        c = snext();
      } while (!isSpaceChar(c));
      return res * sgn;
    }

    public long nextLong() {
      int c = snext();
      while (isSpaceChar(c)) {
        c = snext();
      }
      int sgn = 1;
      if (c == '-') {
        sgn = -1;
        c = snext();
      }
      long res = 0;
      do {
        if (c < '0' || c > '9')
          throw new InputMismatchException();
        res *= 10;
        res += c - '0';
        c = snext();
      } while (!isSpaceChar(c));
      return res * sgn;
    }

    public int[] nextIntArray(int n) {
      int a[] = new int[n];
      for (int i = 0; i < n; i++) {
        a[i] = nextInt();
      }
      return a;
    }

    public String readString() {
      int c = snext();
      while (isSpaceChar(c)) {
        c = snext();
      }
      StringBuilder res = new StringBuilder();
      do {
        res.appendCodePoint(c);
        c = snext();
      } while (!isSpaceChar(c));
      return res.toString();
    }

    public String nextLine() {
      int c = snext();
      while (isSpaceChar(c))
        c = snext();
      StringBuilder res = new StringBuilder();
      do {
        res.appendCodePoint(c);
        c = snext();
      } while (!isEndOfLine(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;
    }

    private boolean isEndOfLine(int c) {
      return c == '\n' || c == '\r' || c == -1;
    }

    public interface SpaceCharFilter {
      public boolean isSpaceChar(int ch);
    }
  }
}

Measured memory_bytes: 8148