using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class aizu_judge
{
    static void Main(string[] args)
    {
        while(true)
        {
            int[] num = Console.ReadLine().Split().Select(int.Parse).ToArray();

            if (num[0] + num[1] == 0)
                break;

            StringBuilder sb = new StringBuilder();

            for (int i = 1; i <= num[0]; i++)
            {
                for(int j = 1; j <= num[1]; j++)
                {
                    sb.Append(i + j % 2 == 0 ? "#" : ".");
                }
                Console.WriteLine(sb.ToString());
            }
            Console.WriteLine();
        }
    }
}