import java.util.Scanner;

class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while(true){
            int h = in.nextInt();
            int w = in.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 ){
                        if(j%2 !=0) {
                            System.out.print("#");
                        }else{
                            System.out.print(".");
                        }
                    }else{
                        if(j%2 !=0){
                            System.out.print(".");
                        }else{
                            System.out.print("#");
                        }
                    }

                }
                System.out.print("\n");
            }
            System.out.print("\n");
        }
    }
}
/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