import java.util.Scanner

object Problem179 {

  def canPaint(move: (Int, Int), sorted: Seq[(Int, Int)], painted: Map[(Int, Int), String]): Boolean = {
    if (sorted.isEmpty) {
      return true
    }
    val from = sorted.head

    painted.get(from) match {
      case None => {
        val to = (move._1 + from._1, move._2 + from._2)
        if (sorted.contains(to)) {
          canPaint(move, sorted.tail, painted + (from -> "RED") + (to -> "BLUE"))
        } else {
          return false
        }
      }
      case _ => canPaint(move, sorted.tail, painted)
    }
  }

  def proc(paintedBlack: Seq[(Int, Int)]): String = {
    val sorted = paintedBlack.sorted

    val painted = sorted.size
    if (painted == 0 || painted % 2 != 0) {
      return "NO"
    }

    // 先頭からの差分をリスト化する
    val (keyX, keyY) = sorted.head
    val moveList = {
      for {
        (x, y) <- sorted.tail
      } yield {
        (x - keyX, y - keyY)
      }
    }

    for (move <- moveList) {
      val ok = canPaint(move, sorted, Map[(Int, Int), String]())
      if (ok) {
        return "YES"
      }
    }
    "NO"
  }

  def main(args: Array[String]) {
    val sc = new Scanner(System.in)
    val (h, w) = (sc.nextInt(), sc.nextInt())

    val paintedBlack = (for (i <- 0 until h) yield {
      sc.next().zipWithIndex.filter(_._1 == '#').map(x => (i, x._2))
    }).flatten

    val result: String = proc(paintedBlack)
    println(result)
  }
}