import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(sc.hasNext()) {
			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 % 2 == 0) {
						if(j % 2 == 0)	System.out.printf("#");
						else	System.out.printf(".");
					}
					else {
						if(j % 2 == 0)	System.out.printf(".");
						else	System.out.printf("#");
					}
				}
				System.out.printf("\n");
			}
			System.out.printf("\n");
		}
	}
}

