what is the lowest price fare from atlanta to san francisco on flight delta 82 and delta 139 
return flights ;return #1 from  atlanta ;return #2 to san francisco ;return #3 equal to delta  82 ;return #3 equal to delta  139 ;return the fares of #4 ;return the fares of #5 ;return the  lowest of #6 ;return the  lowest of #7 ;return #8 , #9
['select', 'filter', 'filter', 'filter', 'filter', 'project', 'project', 'aggregate', 'aggregate', 'union']