A C Puzzle

What code to write in place of "// your code" so that the below code prints 20. Output:

20 

We strongly recommend you to minimize your browser and try this yourself first This question seems to be a trick question, as it is not possible to update local variable in a function without sending it, we can't make value of 'a' as 20 but for outputting 20 we can write function f as below -

2 will be printed by f() and 0 will be printed by a Thanks to Utkarsh Trivedi for suggesting above solution.