import java.util.*;
class Main{
    Scanner sc=new Scanner(System.in);
    void main(){
	while(true){
	    int h=sc.nextInt();
	    int w=sc.nextInt();
	    if(h==0&&w==0)break;
	    for(int i=0;i<h;i++){
		for(int j=0;j<w;j++){
		    if((i+j)%2==0)System.out.print("#");
		    else System.out.print(".");
		}
		System.out.println();
	    }
	    System.out.println();
	}
    }
    public static void main(String[]ag){
	new Main().main();
    }
}
/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