Xor sum-1 need hint

#1

https://hack.codingblocks.com/contests/c/512/562
need a hint

#2

As per the question
Xor sum of array, A, is given by (A1 xor A2 xor …. xor An )

You need to find the maximum xor sum of array
You are allowed to apply the 2 operations as mentioned:-
Choose an index, i.
Add an integer, x to Ai (where -Ai<=x<=Ai ).

Try to think over it. It is a very good and tricky question!!!