import scala.io.Source

object Main extends App {
  for (line <- Source.stdin.getLines if line != "0 0") {
    val Array(h, w) = line.split(" ").map(_.toInt)
    for (i <- 1 to h) {
      for ( j <- 1 to w) {
        print { if ((i+j) % 2 == 0) "#" else "." }
      }
      println()
    }
    println()
  }
}