import java.util.Scanner;
class Main{
 public static void main(String args[]){
  int h,w,i,j;
  Scanner sc = new Scanner(System.in);
  while(true){
   h=sc.nextInt();
   w=sc.nextInt();
   if(h!=0 || w!=0)
    break;
   for(i=0;i<h;i++){
    for(j=0;j<w;j++){
     if((i+j)%2==0)
      System.out.print("#");
     else
      System.out.print(".");}
    System.out.println();}
   System.out.println();}}}
