import java.util.Scanner;

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;
            }

            StringBuilder sb1 = new StringBuilder();
            StringBuilder sb2 = new StringBuilder();

            for (int i = 0; i < w; i++) {
                if ((i % 2) == 0) {
                    sb1.append("#");
                    sb2.append(".");
                } else {
                    sb1.append(".");
                    sb2.append("#");
                }
            }
            

            for (int j = 0; j < h; j++) {
                if ((j % 2) == 0) {
                    System.out.println(sb1);
                } else {
                    System.out.println(sb2);
                }

            }

            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