Find the semester and year which has the least number of student taking any class.
return classes ;return students taking #1 ;return number of #2 for each #1 ;return #1 where  #3 is  lowest ;return semester of  #4 ;return year of  #4 ;return #5 ,   #6
['select', 'project', 'group', 'superlative', 'project', 'project', 'union']