import java.util.Scanner;
public class Chessboad{
	public static  void main(String[] args){

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

}