import scala.io.StdIn._

object Main extends App {
  private def rec(): Unit = {
    val Array(h, w) = readLine().split(" ").map(_.toInt)
    if (h != 0 && w != 0) {
      printBoard(h, w)
      println()
      rec()
    }
  }

  private def printBoard(h: Int, w: Int): Unit =
    (1 to h).foreach { i =>
      (1 to w).foreach { j =>
        if ((i + j) % 2 == 0) print("#") else print(".")
      }
      println()
    }

  rec()
}
