import java.util.*;
import java.io.*;
import java.lang.*;
import java.math.*;
public class Main{
	public static void main(String[] args) throws IOException{
		Scanner stdIn=new Scanner(System.in);
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int h=stdIn.nextInt();
			int w=stdIn.nextInt();
			if(h==0)
				break;
			for(int i=0;i<h;i++){
				if(i%2==0){
					for(int j=0;j<w;j++){
						if(j%2==0)
							System.out.print("#");
						else
							System.out.print(".");
					}
				}
				else{
					for(int j=0;j<w;j++){
						if(j%2==1)
							System.out.print("#");
						else
							System.out.print(".");
					}
					
				}
				System.out.println("");
			}
			System.out.println("");
		}
	}
}
/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