object Main {
  def main(args: Array[String]): Unit = {
    val scanner = new java.util.Scanner(System.in)
    while(true) {
      val h, w = scanner.nextInt
      if((h == 0) && (w == 0)) System.exit(0)

      for(y <- 1 to h) {
        for(x <- 1 to w) {
          print(if(((x + y) % 2) == 0) "#" else ".")
        }
        println()
      }
      println()
    }
  }
}
