import scala.util.control.Breaks
object Main extends App {
  val b = new Breaks()
  b.breakable {
    while (true) {
      val Seq(h, w) = readLine().split(' ').map(_.toInt).toList

      if ((h, w) == (0, 0)) b.break

      val board = for {
        y <- 0 until h

        chs = for {
          x <- 0 until w
        } yield {
          if ( (x + y) % 2 == 0 ) "#" else "."
        }
      } yield {
        chs.reduce(_+_) + "\n"
      }

      board.foreach(print)
      println()
    }
  }
}
