return me the number of papers written by " H. V. Jagadish " , " Yunyao Li " , and " Cong Yu " . 
return papers ;return #1 written by H. V. Jagadish ;return #2 written by Yunyao Li ;return #3 written by Cong Yu ;return number of  #4
['select', 'filter', 'filter', 'filter', 'aggregate']