import java.util.Scanner;

public class Main{
    public static void main(String[]arg){
        Scanner sc = new Scanner(System.in);
            while(true){
              int H = sc.nextInt();
              int W = sc.nextInt();
              if(H==0 && W==0) break;
                 for(int i=0;i<H;i++){
                 for(int j=0;j<W;j++){
                        if((i+j)%2==0){
                         System.out.print("#");
                        }else{
                             System.out.print(".");
                          }
                        }
                 System.out.print("\n");
            }
        }
        System.out.print("\n");
    }
}
