import scala.io.StdIn.readLine

object Main {

  def main(args: Array[String]) = {

    def read:Unit = {
      var n = readLine.split(" ").map(_.toInt)

      if( n(0) != 0 || n(1) != 0) {
        (1 to n(0)).foreach(s=> {
          (1 to n(1)).foreach(t=> {
            if((s+t)%2==0)
              print("#")
            else
              print(".")
          })
          println()
        })
        println()
        read
      }
    }
    read
  }
}