import std.stdio;
import std.conv, std.array, std.algorithm, std.string;
import std.math, std.random, std.range, std.datetime;
import std.bigint;

void main(){
	int h, w;
	{
		int[] tmp = readln.chomp.split.map!(to!int).array;
		h = tmp[0], w = tmp[1];
		}
	
	int count;
	for(int i = 0; i < h; i ++){
		string s = readln.chomp;
		foreach(c; s) if(c == '#') count += 1;
		}
	
	string ans;
	if(count == h + w - 1) ans = "Possible";
	else ans = "Impossible";
	
	ans.writeln;
	}
	
