import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		int H,W;
		
		Scanner scan = new Scanner(System.in);
		while(true)
		{
			H=scan.nextInt();
			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+j)%2==0)
						System.out.printf("#");
					else
						System.out.printf(".");
				}
				
				System.out.printf("\n");
				
			}
			System.out.printf("\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