

import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		//????????£????????????????????°?????????????????£?¨?
				Scanner sc = new Scanner(System.in);
		while(true){
			//???
			int H = sc.nextInt();
			//?¨?
			int W = sc.nextInt();
			//??\?????????0????????????
			if(H ==0 && W ==0){
				break;
			}
			//???????????¶???
			for(int i =1; i <=H; i++){
				//?¨?????????¶???
				String s = "";
				for(int j =1; j<=W; j++){
				//?¨??§??????????
					//????????¶??°??????
					if( i % 2 ==0){
					//?¨??????¶??°?????????
						if(j %2 ==0){
							s += "#";
							//?¨?????\???°??????
						}else{
							s +=".";
						}
						//???????\???°??????
					}else{
						//?¨??????¶??°??????
						if(j % 2==0){
							s +=".";
						//?¨?????\???°??????
						}else{
							s +="#";
						}
					}
				}
				System.out.println(s);
			}
		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