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'.
Example: 10 sottrazione 7
Example solution: 3
Example explanation: Here, 'sottrazione' represents the subtraction operation. So, the answer is 3 (10-7=3).

Problem: 7987 sottrazione 3867 sottrazione 5646 aggiunta 9739 aggiunta 5932 sottrazione 2957 aggiunta 1518 aggiunta 8491

Solution: 21197