instruction: list UA flights from DENVER to SAN FRANCISCO on TUESDAY or WEDNESDAY
response: SELECT DISTINCT flight.flight_id FROM airport_service AS AIRPORT_SERVICE_0, airport_service AS AIRPORT_SERVICE_1, city AS CITY_0, city AS CITY_1, days AS DAYS_0, days AS DAYS_1, flight WHERE ((((flight.flight_days = DAYS_0.days_code AND DAYS_0.day_name = 'TUESDAY') OR (flight.flight_days = DAYS_1.days_code AND DAYS_1.day_name = 'WEDNESDAY')) AND CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'SAN FRANCISCO' AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'DENVER' AND flight.from_airport = AIRPORT_SERVICE_0.airport_code) AND flight.airline_code = 'UA'