object Main {
  def main(args:Array[String]):Unit = {
    for (line <- scala.io.Source.stdin.getLines() if line != "0 0") {
      val Array(h, w) = line.split(" ").map(_.toInt)
      for (i <- 1 to h; j <- 1 to w) {
        if ((i + j) % 2 == 0) {
          print("#")
        } else {
          print(".")
        }
        if (j == w) {
          println()
        }
      }
      println()
    }
  }
}