What are the top 5 countries by number of invoices and how many do they have?
return countries ;return invoices of #1 ;return number of  #2 for each #1 ;return #1 where #3 is highest 5 ;return number of  #2 for each #4 ;return #4 ,  #5
['select', 'project', 'group', 'superlative', 'group', 'union']