import java.util.Scanner;

public class Main {

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        loop: while(true){
            int h = sc.nextInt(),w = sc.nextInt();
            if(w == 0 && h == 0) break loop;
            for(int i = 0;i < h;i++){
                for(int j = 0;j < w;j++){
                    if(i % 2 == 0) System.out.print(j % 2 == 0 ? "#" : ".");
                    else System.out.print(j % 2 == 0 ? "." : "#");
                }
                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