import scala.io.StdIn.readLine

object Main extends App {

  val lines = Iterator.continually(readLine())
  val xs = {
    val xs = for {
      line       <- lines
      Array(h, w) = line.split(" ").map { _.toInt }
    } yield (h, w)

    xs.takeWhile { _ != (0, 0) }
  }

  for {
    rows <- xs.map(solve)
  } {
    rows.foreach(println)
    println()
  }

  def solve(pair: (Int, Int)): Seq[String] = pair match {
    case (h, w) =>
      val s = {
        val sb = StringBuilder.newBuilder
        for {
          i <- 1 to w + 1
          c  = if (i % 2 == 0) '.' else '#'
        } {
          sb += c
        }
        sb.toString
      }

      val oddRow  = s.init
      val evenRow = s.tail

      val rows = for {
        i  <- 1 to h
        row = if (i % 2 == 0) evenRow else oddRow
      } yield row

      rows
  }
}

