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

					}
				}else {
					for(int j=1;j<=W;j++) {
						if(j%2==1) {
							System.out.print(".");
						}else {
							System.out.print("#");
						}

					}

				}
				System.out.println("\n");
			}
		}
	}

}

