show me the flights from boston to pittsburgh leaving wednesdays and thursdays 
return flights ;return #1 from  boston ;return #2 to pittsburgh ;return #3 that  leave on  wednesdays ;return #3 that  leave on  thursdays ;return #3 in both #4 and  #5
['select', 'filter', 'filter', 'filter', 'filter', 'intersection']