import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a,b;
		while(true){
			a = sc.nextInt();
			b = sc.nextInt();
			if(a==0&&b==0)break;
			for(int i=0;i<a;i++){
				for(int j=0;j<b;j++){
					if((i+j)%2==0)System.out.print("#");
					else System.out.print(".");
				}
				System.out.print("\n");
			}
		}
	}
}

