What are the ids of the students who registered for some courses but had the least number of courses for all students?
return students  ;return courses of #1 ;return number of  #2 for each #1 ;return #1 where #3 is higher than zero ;return #4 where #3 is lowest ;return ids of #5
['select', 'project', 'group', 'comparative', 'superlative', 'project']