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.println();
            }
            System.out.println();
        }
    }
}
