
object Main {
  def main(args: Array[String]): Unit = {
    for(line <- io.Source.stdin.getLines() if line != "0 0") {
      val H = line.split(" ")(0).toInt
      val W = line.split(" ")(1).toInt

      for (i <- 0 until H) {
        if (i % 2 == 0) {
          println(("#." * W).substring(0, W))
        }
        else {
          println((".#" * W).substring(0, W))
        }
      }
      println()
    }
  }
}