using System;
using System.Linq;
using System.Text;

namespace ITP1_5_C_Print_a_Chessboard
{
    class Program
    {
        static string buildCheck(int h, int w)
        {
            var even = string.Join( "", Enumerable.Range( 0, w ).Select( i => i % 2 == 0 ? '#' : '.' ) );
            var odd = string.Join( "", Enumerable.Range( 0, w ).Select( i => i % 2 == 0 ? '.' : '#' ) );
            return Enumerable.Range( 0, h ).Select( i => i % 2 == 0 ? even : odd )
                .Aggregate( new StringBuilder(), (acc, s) => acc.AppendLine( s ) ).ToString();
        }
        static void Main(string[] args)
        {
            string[] input = null;
            do
            {
                if ( input != null )
                {
                    var size = input.Select( int.Parse ).ToArray();
                    Console.WriteLine( buildCheck( size[ 0 ], size[ 1 ] ) );
                }
                input = Console.ReadLine().Split( ' ' );
            } while ( input[ 0 ] != "0" || input[ 1 ] != "0" );
        }
    }
}