import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int h,w;

        while(true){
            h=sc.nextInt();
            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%2==0 && j%2==0) || (i%2==1 && j%2==1)){
                        System.out.print("#");
                    }else{
                        System.out.print(".");
                    }
                }
                System.out.print("\n");
            }
            System.out.print("\n");
        }

        sc.close();
    }
}


/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz