import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
import java.util.NoSuchElementException;

public class Main {
	static FastScanner sc = new FastScanner();
	static PrintStream out = System.out;

	public static void main(String args[]) {
		int H = ni();
		int W = ni();
		int a[][] = new int[W][H];
		boolean isAns = false;

		for (int i=0;i<H;i++) {
			String s = next();
			for (int j=0;j<W;j++) {
				a[j][i] = (s.charAt(j) == '#') ? 1 : 0;
			}
		}

		int cnt = 0;
		for (int i=0;i<W;i++) {
			for (int j=0;j<H;j++) {
				if (a[i][j] == 1) {
					cnt++;
				}
			}
		}

		if (cnt == H + W - 1) {
			// search route
			isAns = search(a, W, H, 0, 0);
		}

		System.out.println(isAns ? "Possible" : "Impossible");
	}

	private static boolean search(int a[][], int W, int H, int x, int y) {
		if (x == W-1 && y == H-1) return true;

		boolean ret = false;
		if (x < W-1) {
			if (a[x+1][y] == 1) {
				ret |= search(a, W, H, x+1, y);
			}
		}
		if (y < H-1) {
			if (a[x][y+1] == 1) {
				ret |= search(a, W, H, x, y+1);
			}
		}

		return ret;
	}

	private static String next() {
		return sc.next();
	}

	private static int ni() {
		return sc.nextInt();
	}

	private static long nl() {
		return sc.nextLong();
	}

	private static int[] na(int n) {
		int[] a = new int[n];
		for(int i = 0;i < n;i++) a[i] = ni();
		return a;
	}

	private static long[] nal(int n) {
		long[] a = new long[n];
		for(int i = 0;i < n;i++) a[i] = ni();
		return a;
	}

	private static double nd() {
		return Double.parseDouble( next() );
	}
}

class FastScanner {
	private final InputStream in = System.in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
	public boolean hasNext() { skipUnprintable(); return hasNextByte();}
	public String next() {
		if (!hasNext()) throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public int nextInt() {
		if (!hasNext()) throw new NoSuchElementException();
		int n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public long nextLong() {
		if (!hasNext()) throw new NoSuchElementException();
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
}


Measured memory_bytes: 8276