import java.util.*;
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++) {
               int cnt = i%2;
              for (int j = 0; j < W; j++) {
                if(cnt %2 ==0)
                {
                    System.out.print("#");
                }
                else{
                    System.out.print(".");
                }
                cnt ++;
              } 
              System.out.println();

           }
           System.out.println();
        }
        sc.close();
    }
}

/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