object Main extends App {
  val sc = new java.util.Scanner(System.in)
  printChessboard(sc.nextInt(), sc.nextInt())

  def printChessboard(h: Int, w: Int): Unit = {
    (h, w) match {
      case (0, 0) => sc.close()
      case _ =>
        for (i <- 1 to h) i match {
          case _ if i % 2 != 0 => printOddRow(w)
          case _ if i % 2 == 0 => printEvenRow(w)
        }
        println()
        printChessboard(sc.nextInt(), sc.nextInt())
    }
  }

  def printOddRow(w: Int): Unit = {
    for (i <- 1 to w) i match {
      case _ if i % 2 != 0 => print("#")
      case _ if i % 2 == 0 => print(".")
    }
    print("\n")
  }

  def printEvenRow(w: Int): Unit = {
    for (i <- 1 to w) i match {
      case _ if i % 2 != 0 => print(".")
      case _ if i % 2 == 0 => print("#")
    }
    print("\n")
  }
}