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 = 1;i <= H;i++) {
				for(int j = 1;j <= W;j++) {
					if(i%2 == j%2) {
						System.out.printf("#");
					} else {
						System.out.printf(".");
					}
				}
				System.out.printf("\n");
			}
			System.out.printf("\n");
		}
	}
}

