Find the Single Number

Given an array of integers where every element appears exactly twice except for one, find that single element. This is a classic problem that can be efficiently solved using the bitwise XOR operation. Note that the XOR operation satisfies the properties $$a \oplus a = 0$$ and $$a \oplus 0 = a$$, which means that pairing up the repeated numbers will cancel them out, leaving the unique number.

The input is provided via standard input (stdin) and the output should be printed to standard output (stdout).

inputFormat

The first line contains a single integer $$n$$, representing the number of elements in the array. The second line contains $$n$$ space-separated integers.

outputFormat

Output a single integer which is the element that appears only once.

3
2 2 1

1