import scala.io.StdIn.readLine

object Main extends App {

  for (_ <- 1 to 300) {
    val input = readLine.split(" ").map(_.toInt)
    val (h, w) = (input(0), input(1))

    if (h == 0 && w == 0) sys.exit() else {
      for (e <- 1 to h) {
        var line = scala.collection.mutable.ArrayBuffer[String]()
        // 奇数行
        if (e % 2 == 1) for (e <- 1 to w) {
          if (e % 2 == 1) line += "#" else line += "."
        }
        // 偶数行
        else for (e <- 1 to w) {
          if (e % 2 == 1) line += "." else line += "#"
        }
        println(line.mkString)
      }
      println()
    }
  }

}

