/**
  * http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_5_C
  * Structured Program I - Print a Chessboard
  */
object Main {
  def main(args: Array[String]): Unit = {
    Iterator.continually(io.StdIn.readLine()).takeWhile(_ != null).map(_.split(" ").map(_.toInt))
      .map { case Array(h, w) => (h, w) }
      .takeWhile(_ != (0, 0))
      .map { case (h, w) => createAChessBoard(h, w) }
      .foreach(_.foreach(println))
  }

  def createAChessBoard(h: Int, w: Int): Seq[String] = {
    (1 to h).map(
      y => (1 to w).foldLeft("") {
        (line, x) => line + (if (x % 2 == y % 2) "#" else ".")
      }
    ) :+ ""
  }
}