Which had less troops, the Bulgarian 2nd Army or the two Serb divisions?
return troops ;return #1 of the  Bulgarian 2nd Army ;return #1 of the  two Serb divisions ;return number of  #2 ;return number of  #3 ;return which is lowest of #4 ,  #5
['select', 'filter', 'filter', 'aggregate', 'aggregate', 'comparison']