object Main extends App {
	override def main(args: Array[String]) = {
		val sc = new java.util.Scanner(System.in)
		
		val pw = new java.io.PrintWriter(System.out);
		
		Iterator.continually(new Rectangle(sc.nextInt,sc.nextInt))
			.takeWhile(_.isContinue)
			.foreach(_.print(pw))

		pw.flush
		
	}
	
	class Rectangle(val H: Int, val W:Int){
		val isContinue = !(H == 0 && W == 0)
		
		def print(pw : java.io.PrintWriter):Unit = {
			for(i <- (1 to H)){
				for(j <- (1 to W)){
					(i,j) match{
						case (n,m) if (n + m) % 2 == 0 =>
							pw.print("#")
						case (_,_) => 
							pw.print(".")
					}
				}
				pw.println
			}
			pw.println
		}
		
	}
}