import java.util.Scanner;
class Main{
    public static void main(String[] args){
		int H,W;
		Scanner sc=new Scanner(System.in);
		while(true){
			H=sc.nextInt();
			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==0){
						System.out.print("#");
					}else System.out.print(".");
				}
				System.out.println("");
			}
			System.out.println("");
		}
    }
}

