import java.util.Scanner;
public class Main {
public static void main(String[] args) {
	Scanner sc=new Scanner(System.in);
	while(sc.hasNext()) {
		int H=sc.nextInt();
		int W=sc.nextInt();
		if(H==0 && W==0) {
			break;
		}else {
			for(int i=0;i<H;i++) {
				for(int j=0;j<W;j++) {
if((i%2!=0 && j%2!=0)||(i%2==0 && j%2==0)){
	System.out.print("#");
}else {
	System.out.print(".");
}
				}
				System.out.println();
			}
		}
	}
}
}
