import java.util.*;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(true){
		int H = scan.nextInt();
		int W = scan.nextInt();
		if(H==0&&W==0) break;
		for(int i=0; i<H; i++){
			for(int j=0; j<W; j++){
				if(i%2==0){
					if(j%2==0) System.out.print("#");
					else System.out.print(".");
				}
				else {
					if(j%2==0) System.out.print(".");
					else System.out.print("#");
				}
			}
			System.out.println();
		}
		System.out.println();
		
		}
	}

}