import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        int i ,j;

        while(true){
            int H = sc.nextInt();
            int W = sc.nextInt();

            if(H == 0  && W == 0)break;

            for(i = 0;i < H;i++){
                for(j = 0;j < W;j++){
                    if(i % 2 == 0 && j % 2 == 0 || i % 2 == 1 && j % 2 == 1){
                        System.out.printf("#");
                    }else{
                        System.out.printf(".");
                    }
                }

                System.out.printf("\n");

            }

            System.out.printf("\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