fun main(args: Array<String>) {
    val (h, w) = readLine()!!.split(" ").map { it.toInt() }
    var cnt = 0
    for (i in 0 until h) {
        cnt += readLine()!!.count { it == '#' }
    }
    if (cnt==h+w-1) println("Possible")
    else println("Impossible")
}