Find the number of students who are older than 18 and do not have allergy to either food or animal.
return students ;return #1 that  are  older than  18 ;return #1 that  do not  have  allergy to  food ;return #1 that  do not  have  allergy to  animal ;return #3 , #4 ;return #1 of  both #2 and #5 ;return number of #6
['select', 'filter', 'filter', 'filter', 'union', 'intersection', 'aggregate']