import io.Source.stdin

object Main {

  def main(args: Array[String]) {
    for ((list) <- stdin.getLines().takeWhile(_ != "0 0").map(_.split(" ").map(_.toInt))) {
      val (h: Int, w: Int) = (list(0), list(1))
      printChessBoard(h, w)
    }
  }

  def printChessBoard(h: Int, w: Int) {
    for (i <- 1 to h) {
      for (j <- 1 to w) {
        printChar(isSharp(i, j))
      }
      println()
    }
    println()
  }
  
  def printChar(isSharp: Boolean) {
    if (isSharp) {
      print("#")
    } else {
      print(".")
    }
  }
  
  def isSharp(i: Int, j: Int): Boolean = {
    if ((i % 2 == 0 && j % 2 != 0) || (j % 2 == 0 && i % 2 != 0)) {
      false
    } else {
      true
    }
  }
}
