import java.text.*;
import java.math.*;
import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int[] num= new int[2];

		while(true) {
			num[0] = scan.nextInt();
			num[1] = scan.nextInt();
			if(num[0] == 0) break;
			for(int i1 = 0; i1 < num[0];i1++) {
				for(int i2 = 0;i2 < num[1];i2++) {
					if(i1 % 2 != 0) {
						if(i2 % 2 == 0) {
							System.out.print(".");
						}else {
							System.out.print("#");
						}
					}else {			
						if(i2 % 2 == 0) {
							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