import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int j = 0;
            int H = sc.nextInt();
            int W = sc.nextInt();
            if (H == 0 && W == 0) {
                break;
            }
            for (int i = 0; i < H; i++) {
                for (int k = 0; k < W; k++) {
                    if ((i + k) % 2 == 1) {
                        System.out.printf("#");
                    } else {
                        System.out.printf(".");
                    }
                }
                System.out.printf("\n");
            }
            System.out.printf("\n");
        }
        sc.close();
    }
}
