object Main {
  def Print(x:Int,y:Boolean){
    var char=y
    for(i<-1 to x){
      if(char){
        print("#")
        char=false
      }
      else{
        print(".")
        char=true
      }
    }
    println()
  }
  def main(args:Array[String]){
    val sc=new java.util.Scanner(System.in)
    var tmp=false  
      while(true){
       val h,w=sc.nextInt
       var check=true
       if(tmp) println()
       if(h==0&&w==0) return
       for(i<-1 to h){
         Print(w,check)
         if(check) check=false
         else check=true
       }
       tmp=true
     }
  }
}