import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
// dfmt on

void main()
{
    long H, W;
    scan(H, W);
    auto A = new string[](H);
    foreach (i; 0 .. H)
        A[i] = sread();

    foreach (x; 2 .. W)
        if (A[0][x] == '#')
        {
            writeln("Impossible");
            return;
        }

    foreach (y; 1 .. H)
        foreach (x; 0 .. W)
            if (A[y][x] == '#')
            {
                if (x != y && x != y + 1)
                {
                    writeln("Impossible");
                    return;
                }
                if (A[y][x - 1] != '#' && A[y - 1][x] != '#')
                {
                    writeln("Impossible");
                    return;
                }
            }
    writeln("Possible");
}
