import scala.io.{StdIn => in}

object Main extends App {
  val Array(h, w) = in.readLine.split(" ").map(_.toInt)
  val grid = Iterator.continually(in.readLine)
    .take(h)
    .map(_.map(ch => if(ch == '.') true else false).toArray)
    .toArray
  
  val dx = Array(0, 1, 0, -1)
  val dy = Array(1, 0, -1, 0)

  val ans = {
    var isPossible = true
    val check = (i:Int, j:Int, k:Int) =>
      0 <= i + dy(k) && i + dy(k) < h &&
        0 <= j + dx(k) && j + dx(k) < w

    for {
      i <- 0 until h
      j <- 0 until w
      if isPossible && !grid(i)(j)
    } {
      isPossible = 
      (0 until 4)
        .map(k => if(check(i,j,k)) !grid(i+dy(k))(j+dx(k)) else false )
        .exists(_ == true)
    }
    if(isPossible) "Yes" else "No"
  }

  println(ans)
}