import java.util.*;

public class Main{
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		int H,W;	
		int i,j;

		while(true) {
			H = sc.nextInt();
			W = sc.nextInt();
			
			if (H==0 && W==0) {
				break;
			}
			
			for (i=0 ; i<H ; i++) {
				for (j=0 ; j<W ; j++) {
					if ((i+j)%2==0) {
						System.out.printf("#");
					}else {
						System.out.printf(".");
					}
				}
				System.out.printf("\n");
			}
			System.out.printf("\n");
		}
		sc.close();
	}
	
}
