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