import scala.io.StdIn.readLine

object Main {

  def main(args: Array[String]) = {

    var n = readLine.split(" ").map(_.toInt)
    while( n(0) != 0 || n(1) != 0) {
      val h = n(0)
      val w = n(1)

      for(i <- 0 to h-1) {
        for(j <- 0 to w-1) {
          if((i+j)%2==0)
            print("#")
          else
            print(".")
        }
        println()
      }
      println()
      n = readLine.split(" ").map(_.toInt)
    }
  }
}