english-39 Apears an Odd Number of Times

描述

Given a sequence of N numbers. Find X that the number of X’s in the sequence is odd.

输入

First line: one positive integers N (N <= 100).Second line: N positive integers (<= 10000).

输出

One integer X.

样例输入

1
27
2 4 4 3 3 2 2

样例输出

12

限制

• 时间限制：1000ms
• 内存限制：128MB