What is the name of every city that has at least 15 stations and how many stations does it have?
return cities ;return stations in #1 ;return number of  #2 for each  #1 ;return #1 where #3 is  at least 15 ;return names of  #4 ;return stations in #4 ;return number of  #6 for each  #4 ;return #5 ,  #7
['select', 'project', 'group', 'comparative', 'project', 'project', 'group', 'union']