import java.util.Scanner;

class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		for(;;){
			int H = scan.nextInt();
			int W = scan.nextInt();
			if(H == 0 && W == 0){
				scan.close();
				break;
			}

			for(int i = 0; i < H; i++){ //縦の列の繰り返し
				if(i%2 == 0){
					for(int s=0; s<W; s++){ //偶数列の横の行の繰り返し
						if(s%2 == 0)
							System.out.print("#");
						else
							System.out.print(".");
					}
				}else{
					for(int t=0; t<W; t++){ //奇数列の横の行の繰り返し
						if(t%2 == 0)
							System.out.print(".");
						else
							System.out.print("#");
					}
				}
				System.out.print("\n");
			}
			System.out.print("\n");
		}
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz