
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();

		}
		
		sc.close();
	}
}

