The Lonely Number

Easy#bit-manipulation #xor· solved by 0 · time limit 2.0 s

Every value appears exactly twice except one, which appears once. Find it using $O(1)$ extra memory (hint: XOR).

Input

$n$ (odd), then $n$ integers.

The single value.

$1 \le n \le 10^5$

Input

5
4 1 2 1 2

Output

Input

1
7

Output