import java.util.Scanner;

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

        while(true) {
            int H = sc.nextInt();
            int 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 + j) % 2 == 0) System.out.print('#');
                    else System.out.print('.');
                }
                System.out.print("\n");
            }
            System.out.print("\n");
        }
    }
}
