List the name and the number of stations for all the cities that have at least 15 stations.
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']