import java.util.Scanner;

public class itp_5_c {
	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++){
				
				if(i%2==0){//偶数行は#.#.
					for(int j=0;j<W;j++){
						if(j%2==0)System.out.print("#");
						else System.out.print(".");
					}
				}
				else {//奇数は.#.#
					for(int j=0;j<W;j++){
						if(j%2==0)System.out.print(".");
						else System.out.print("#");
					}
				}
				System.out.println();
				
			}
			System.out.println();
		}
	}
}
