import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Scanner in = new Scanner(System.in);
		while(in.hasNext()){
		int H = in.nextInt();
		int W = in.nextInt();
		if(H==0&&W==0){
			break;
		}
		for(int i = 0; i<H ; i++){
			for(int j = 0; j<W ; j++){
				if(i%2==1&&j%2==0||i%2==0&&j%2==1){
					System.out.print(".");
				}else{
					System.out.print("#");
							}
						}
					System.out.println();
					}
					System.out.println();
				}
			}
		}