How many in all were in the Russian army and Left Bank Cossacks that were headed to Perekop in May 1687?
return the  Russian army ;return #1 that was  headed to Perekop ;return #2 in   May 1687 ;return size of #3 ;return Left Bank Cossacks ;return #5 that were headed to Perekop ;return #6 in   May 1687 ;return number of  #7 ;return sum of #4 and  #8
['select', 'filter', 'filter', 'project', 'select', 'filter', 'filter', 'aggregate', 'arithmetic']