#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0;i < n;i++)
using ll = long long;

int main(){
  int h,w; cin >>h >>w;
  int cnt = 0;
  rep(i,h){
    string s; cin >>s;
    rep(j,w) if(s[j]=='#') cnt++;
  }
  if(cnt==h+w-1) cout << "Possible" << endl;
  else cout << "Impossible" << endl;
  return 0;
}