while true
	h, w = gets.split( " " ).map { | val | val.to_i }
	break if 0 == h && 0 == w
	
	h.times { | i |
		if 0 == i%2
			w.times {  | i |
				if 0 == i%2
					print( "#" )
				else
					print( "." )
				end
			}
			print( "\n" )
		else
			w.times {  | i |
				if 0 == i%2
					print( "." )
				else
					print( "#" )
				end
			}
			print( "\n" )
		end
	}
	print( "\n" )
end