import java.util.Scanner;
class Main{
    public static void main(String[] args){
	final Scanner sc=new Scanner(System.in);
	while(true){
	int a=sc.nextInt();
	int b=sc.nextInt();
	if(a==0 && b==0) break;
	for(int i=0;i<a;i++){
	    for(int j=0;j<b;j++){
		if((i+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