
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;
			}else {
				for(int i=0;i<H;i++) {
					for(int j=0;j<W;j++) {
						if(i%2==0) {
						if(j%2==0) {
							System.out.print("#");
						}else {
							System.out.print("。");
						}
						}else {
							if(j%2==1) {
								System.out.print("#");
							}else {
								System.out.print("。");
							}
						}
					}
					System.out.println("");
				}
			}
		}
	}
}

