import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        int i,k;

        while(true)
        {
            int H = sc.nextInt();
            int W = sc.nextInt();
    
            if(H==0 && W==0) break;

            for(i=0; i<H; i++)
            {
                for(k=0; k<W; k++)
                {
                    if(i%2 == 0)
                    {
                        if(k%2==0) System.out.printf("#");
                        else if(k%2==1) System.out.printf(".");
                    }                
                    else if(i%2 == 1)
                    {
                        if(k%2==0) System.out.printf(".");
                        else if(k%2==1) System.out.printf("#");
                    }
                }
                System.out.print("\n");
            }

            System.out.printf("\n");
        }

        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