#include<bits/stdc++.h>
using namespace std;
int main(){
    int h, w;
    scanf ("%d %d", &h, &w);
    int cnt = 0;
    for (int i = 1; i <= h; ++i) {
        getchar ();
        for (int j = 1; j <= w; ++j) {
            char ch=getchar ();
            if (ch=='#') ++cnt;
        }
    }
    puts((cnt==h+w-1)?"Possible":"Impossible");
    return 0;
}