In this task you will be given an arithmetic operation in Italian and you have to find its answer. The operations 'addition' and 'subtraction' have been replaced with their italian translations i.e you need to perform addition when you see 'aggiunta' and subtraction in case of 'sottrazione'.
Q: 6564 sottrazione 8635 sottrazione 159 sottrazione 6435 aggiunta 2739 aggiunta 3755
A: 
-2171