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