import java.util.Scanner;
public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);


        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();

            if (w == 0 && h == 0) break;
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    if (i % 2 == 0) System.out.printf("#.");
                    else System.out.printf(".#");
                }
                System.out.printf("\n");
            }
            System.out.printf("\n");
        }
    }
}
