import java.util.*
import kotlin.math.acos
import kotlin.math.cos
import kotlin.math.round
import kotlin.math.sin

fun main(args: Array<String>) {
    val (h, w) = readIntList()
    val a = List(h) { readString() }

    var cnt = 0
    for (i in 0 until h) {
        for (j in 0 until w) {
            if (a[i][j] == '#') cnt++
        }
    }
    if (cnt == h + w - 1) println("Possible")
    else println("Impossible")
}

// read
fun readString() = readLine()!!
fun readInt() = readLine()!!.toInt()
fun readLong() = readLine()!!.toLong()
fun readStringList() = readLine()!!.split(" ")
fun readIntList() = readLine()!!.split(" ").map(String::toInt)
fun readLongList() = readLine()!!.split(" ").map(String::toLong)