import java.util.*;

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 == 1) {
                        if (j % 2 == 1) {
                            System.out.print("#");
                        } else {
                            System.out.print(".");
                        }
                    } else {
                        if (j % 2 == 1) {
                            System.out.print(".");
                        } else {
                            System.out.print("#");
                        }
                    }
                }
                System.out.println();
            }
            System.out.println();
        }
        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