object Main {
  val Pattern = Array('#', '.')

  def main(args: Array[String]): Unit = {
    Iterator.continually(io.StdIn.readLine())
      .map { line =>
        val arr = line.split(" ").map(_.toInt)
        (arr(0), arr(1))
      }
      .takeWhile {
        case (0, 0) => false
        case _ => true
      }
      .foreach { case (h, w) =>
        val sb = StringBuilder.newBuilder
        for (y <- 0 until h) {
          val base = y % 2
          for (x <- 0 until w) {
            sb.append(Pattern((base + x) % 2))
          }
          sb.append('\n')
        }
        sb.append('\n')
        print(sb.toString())
      }
  }
}