import java.util.Scanner;

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

        while (true) {
            int H = scan.nextInt(), W = scan.nextInt();
            if (H == 0 && W == 0) break;

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

    }

}
/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