what is the earliest flight from denver to san francisco on the morning of august twenty seventh
O O O B-flight_mod O O B-fromloc.city_name O B-toloc.city_name I-toloc.city_name O O B-depart_time.period_of_day O B-depart_date.month_name B-depart_date.day_number I-depart_date.day_number