object Main {
  def main(args:Array[String]): Unit = {
    Iterator.continually(readLine())
      .map(s => {
        val xs = s.split(" ").map(_.toInt)  
        (xs(0), xs(1))
      })
      .takeWhile{
        case (0,0) => false
        case _ => true
      }
      .foreach(xs => {
        val h = xs._1
        val w = xs._2
       
        var st = ""
        for (i <- 1 to h){
          if (i % 2 == 0) st += getChessboard(1 to w)("#")(".") + "\n"
          else st += getChessboard(1 to w)(".")("#") + "\n"
        }
        println(st)
      })
  }

  def getChessboard(r:Range)(even:String)(odd:String): String = {
    r.foldLeft(""){
        case (a, i) if (i % 2 == 0) => a + even 
        case (a, _) => a + odd
    }
  }
}