Given an array of integers, where all elements but one occur twice, find the unique element.

Example

$a=[1,2,3,4,3,2,1]$

The unique element is $\begin{array}{c}4\end{array}$.

Function Description

Complete the lonelyinteger function in the editor below.

lonelyinteger has the following parameter(s):

int a[n]: an array of integers

Returns

int: the element that occurs only once

Input Format

The first line contains a single integer, $n$, the number of integers in the array.

The second line contains $n$ space-separated integers that describe the values in $\boldsymbol{a}$.

Constraints

$1\leq n<100$
It is guaranteed that $n$ is an odd number and that there is one unique element.
$0\leq a[i]\leq100$, where $0\leq i<n$.

Sample Input 0
1
1

Sample Output 0
1

Explanation 0

There is only one element in the array, thus it is unique.

Sample Input 1
3
1 1 2

Sample Output 1
2

Explanation 1

We have two $\mbox{1}$'s, and $2$ is unique.

Sample Input 2
5
0 0 1 2 1

Sample Output 2
2

Explanation 2

We have two $\mbox{0}$'s, two $\mbox{1}$'s, and one $2$. $2$ is unique.

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