object Main extends App {
  val scanner = new java.util.Scanner(System.in)

  val data = Iterator.continually {
    val H  = scanner.nextInt()
    val W  = scanner.nextInt()

    (H, W)
  }

  val outputs = data.takeWhile(_ != (0, 0)).map {
    case (h, w) =>
      (1 to h).map { hp =>
        (1 to w).map { wp =>
          if((hp % 2 ^ wp % 2) == 0) "#"
          else                       "."
        }.mkString
      }.mkString("\n")
  }

  outputs.foreach(println)
}