import java.util.*;

public class Main {

	public static void  main(String[] args) {
		scan();
		
		
		
	}
	
	public static void scan() {
		Scanner scanner = new Scanner(System.in);
		while(true){
			int H = scanner.nextInt();
			int W = scanner.nextInt();
			if(H == 0 && W == 0){
				break;
			}
			draw(H , W);
			System.out.println("");
		}	
		scanner.close();
		return;
	}

	public static void draw(int  H , int W) {
		for(int y = 0 ; y < H ; y++){	
			for(int x = 0 ; x < W ; x++){
				if(y % 2 == 0){
					if(x % 2 == 0){
						System.out.print("#");
					}
					else{
						System.out.print(".");
					}
				}
				else{
					if(x % 2 != 0){
						System.out.print("#");
					}
					else{
						System.out.print(".");
					}
				}	
			}
			System.out.println("");
		}
		return ;
	}
	
}
/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