import java.io.*;
import java.util.*;

class Main
{
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        
        int H = sc.nextInt();
        int W = sc.nextInt();
        
        while (H != 0 || W != 0) {
            for (int i = 0; i < H; i++) {
                for (int j = 0; j < W; j++) {
                    if ((i % 2 == 0 && j % 2 == 0) || (i % 2 == 1 && j % 2 == 1)) {
                        System.out.printf("#");
                    }
                    else {
                        System.out.printf(".");
                    }
                }
                System.out.printf("\n");
            }
            System.out.printf("\n");
            
            H = sc.nextInt();
            W = sc.nextInt();
        }
    }
}
/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