import scala.io.Source

object Main {
  def main(args:Array[String]) {
    
    for(line <- Source.stdin.getLines()) {
      val items = line.split(" ").toList.map(_.toInt)
      if (items(0) == 0 && items(1) == 0) {
        return      
      }
      
      for (hIndex <- (1 to items(0))) {
        val w = (1 to items(1)).toList.map{ wIndex => 
          if ((hIndex % 2 == 0 && wIndex % 2 != 0) || (hIndex % 2 != 0 && wIndex % 2 == 0)) "#" 
          else "."
        }
        println(w.mkString)
      }
    }
  }
}