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

public class Test
{
	static public void Main( )
	{
		StringBuilder output = new StringBuilder();
		while( true ) { 
			String[] data = Console.ReadLine().Split( ' ' );
			var H = Int32.Parse( data[0] );
			var W = Int32.Parse( data[1] );
			if( 0 == H && 0 == W ) break;
			
			var w = String.Concat( Enumerable.Repeat( "#.", 152 ) );
			for( var i=0; i<H; i++ ) {
				output.Append( w.Substring( (i&1), W ) ).Append( "\n" );
			}
			output.Append( "\n" );
			Console.Write( output );
			output.Clear();
		}
	}
}