723. Unique Element

0

Easy

Given an array of integers where every element appears twice except for one, find the unique element.

Input Format

The first line of the input consists of an integer N, representing the size of the array. This is followed by N integers, which are the elements of the array.

Output Format

Print the element that appears only once.

Example

Input

5 4 4 1 1 2

Output

2

Constraints

0 < N <= 100000000
0 <= A[i] <= 10000000000
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