import scala.io.StdIn

object Main {
  def main(args: Array[String]): Unit = {
    val inputs = Iterator.continually(StdIn.readLine()).takeWhile(_ != null)
    for{
      in <- inputs
      val Array(h, w, _*) = in.split(" ").map(_.toInt)
      }{
        if(h != 0 && w != 0){
          println((List.tabulate(h, w){(i, j) =>
            val isSharp = (i % 2 == 0 && j % 2 == 0) || (i % 2 != 0 && j % 2 != 0)
            val isDot = !isSharp
            val EOL = j == w-1

            if(isSharp && EOL) "#\n"
            else if(isDot && EOL) ".\n"
            else if(isSharp) "#"
            else "."
          }).flatten.mkString)
        }
      }
  }
}