import scala.io.StdIn.readLine

object Main {
	def main(args: Array[String]) = {
		var a = readLine.split(" ").map(_.toInt)
		
		while(a(0) != 0 || a(1) != 0) {
			val s1 = "#." * a(1)
			val s2 = ".#" * a(1)
			
			for(i <- 0 to a(0)-1) {
			if(i % 2 == 0)
				println(s1.take(a(1)))
			else
				println(s2.take(a(1)))
			}
			println()
			a = readLine.split(" ").map(_.toInt)
		}
	}
}