Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.
Compute the xor sum of the elements that appear an odd number of times in the array a.
Input
The first line contains number n (1 ≤ n ≤ 3000000). The second line of the input contains n numbers, representing the array a. All elements of a are between 0 and 109
Output
The only line of the output contains the answer of the problem.