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();
        if ( H == 0 || W == 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 == 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