import java.util.NoSuchElementException

fun main(args: Array<String>) = FastScanner().run {
    val h = nextInt()
    val w = nextInt()
    val a = Array(h){next().toCharArray()}
    var p = Pair(0, 0)
    outer@while (true) {
        a[p.first][p.second] = '.'
        for (next in adjacent2(p.first, p.second, h, w)) if (a[next.first][next.second] == '#') {
            p = next
            continue@outer
        }
        break
    }

    var possible = true
    for (y in 0 until h)
        for (x in 0 until w)
            if (a[y][x] == '#') possible = false
    if (possible) println("Possible") else println("Impossible")
}

fun adjacent2(y: Int, x: Int, h: Int, w: Int): List<Pair<Int, Int>> {
    return listOf(Pair(1, 0), Pair(0, 1)).mapNotNull {
        val ny = y + it.first
        val nx = x + it.second
        if (nx in 0 until w && ny in 0 until h) {
            Pair(ny, nx)
        } else null
    }
}

class FastScanner {
    private val printable = 33..126
    val `in` = System.`in`
    val buffer = ByteArray(1024)
    var ptr = 0
    var buflen = 0
    fun hasNextByte(): Boolean {
        if (ptr < buflen) {
            return true
        } else {
            ptr = 0
            buflen = `in`.read(buffer)
            if (buflen <= 0) {
                return false
            }
        }
        return true
    }
    fun readByte(): Byte {
        return if (hasNextByte()) buffer[ptr++] else return -1
    }
    fun hasNext(): Boolean {
        while (hasNextByte() && buffer[ptr] !in printable) ptr++
        return hasNextByte()
    }
    fun next(): String {
        if (!hasNext()) throw NoSuchElementException()
        val sb = StringBuilder()
        var b = readByte()
        while (b in printable) {
            sb.appendCodePoint(b.toInt())
            b = readByte()
        }
        return sb.toString()
    }
    fun nextLong(): Long {
        if (!hasNext()) throw NoSuchElementException()
        var n = 0L
        var minus = false
        var b = readByte()
        if (b == '-'.toByte()) {
            minus = true
            b = readByte()
        }
        if (b !in '0'.toByte()..'9'.toByte()) {
            throw NumberFormatException()
        }
        while (true) {
            if (b in '0'.toByte()..'9'.toByte()) {
                n *= 10
                n += b - '0'.toByte()
            } else if (b == (-1).toByte() || b !in printable) {
                return if (minus) -n else n
            } else {
                throw NumberFormatException()
            }
            b = readByte()
        }
    }
    fun nextInt(): Int {
        val nl = nextLong()
        if (nl !in Integer.MIN_VALUE..Integer.MAX_VALUE) throw NumberFormatException()
        return nl.toInt()
    }
    fun nextDouble(): Double {
        return next().toDouble()
    }
}