import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        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.printf("\n");
                }
                System.out.printf("\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