import std.stdio, std.string, std.conv;
import std.range, std.algorithm, std.array;


void main() {
    int h, w;
    scan(h, w);

    auto map = new char[][](h, w);
    iota(h).each!(i => map[i] = readln.chomp.to!(char[]));

    if (map[0][0] != '#') {
        writeln("Impossible");
        return;
    }

    int pi, pj;

    while (!(pi == h-1 && pj == w-1)) {
        int ni = pi + 1, nj = pj;
        if (ni < h && map[ni][nj] == '#') {
            map[pi][pj] = '.';
            pi = ni, pj = nj;
            continue;
        }
        ni = pi, nj = pj + 1;
        if (nj < w && map[ni][nj] == '#') {
            map[pi][pj] = '.';
            pi = ni, pj = nj;
            continue;
        }
        writeln("Impossible");
        return;
    }

    if (map[h-1][w-1] != '#') {
        writeln("Impossible");
        return;
    }

    map[h-1][w-1] = '.';

    debug {
        writefln("%(%-(%s %)\n%)", map);
    }

    foreach (i ; 0 .. h) {
        foreach (j ; 0 .. w) {
            if (map[i][j] == '#') {
                writeln("Impossible");
                return;
            }
        }
    }

    writeln("Possible");
    return;
}



void scan(T...)(ref T args) {
    import std.stdio : readln;
    import std.algorithm : splitter;
    import std.conv : to;
    import std.range.primitives;

    auto line = readln().splitter();
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}



void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}
