object Main {
    import scala.annotation.tailrec

    def main(args: Array[String]) = {
        val sc = new java.util.Scanner(System.in)
        val dots = Array("#", ".")

        drawPlaid(sc, dots)
    }

    def drawPlaid(scanner: java.util.Scanner, dotset: Array[String]): Unit = {
        val h, w = scanner.nextInt

        if( h != 0 && w != 0 ) {
            for( i <- 0 until h ) {
                for( j <- 0 until w ) print(dotset((i+j)%2))
                print("\n")
            }
            print("\n")

            drawPlaid(scanner, dotset)
        }

    }

}

