import java.util.Scanner;

public class Main{
	public static void main(String[] args){

		Scanner scan = new Scanner(System.in);

		while(true){
			int h = scan.nextInt();
			int w = scan.nextInt();

			if(h == 0 && w == 0){
				 break;
			}else{
				for(int a = 0; a < h; a++){
					for(int b = 0; b < w; b++){
						if(a % 2 == 0){
							if(b % 2 == 0){
								System.out.print("#");
							}else{
								System.out.print(".");
							}
						}else{
							if(b % 2 == 0){
								System.out.print(".");
							}else{
								System.out.print("#");
							}
						}
					}
					System.out.println();
				}
				System.out.println();
			}
		}
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz