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 str1 = "#."*n(1)
      val str2 = ".#"*n(1)

      for(i <- 0 to n(0)-1) {
        if(i%2==0)
          println(str1.take(n(1)))
        else
          println(str2.take(n(1)))
      }
      println()
      n = readLine.split(" ").map(_.toInt)
    }
  }
}