Lovely Palindromes

题意翻译

给你一个数$n$，求第$n$小的偶数位回文数

题目描述

Pari has a friend who loves palindrome numbers. A palindrome number is a number that reads the same forward or backward. For example $ 12321 $ , $ 100001 $ and $ 1 $ are palindrome numbers, while $ 112 $ and $ 1021 $ are not. Pari is trying to love them too, but only very special and gifted people can understand the beauty behind palindrome numbers. Pari loves integers with even length (i.e. the numbers with even number of digits), so she tries to see a lot of big palindrome numbers with even length (like a $ 2 $ -digit $ 11 $ or $ 6 $ -digit $ 122221 $ ), so maybe she could see something in them. Now Pari asks you to write a program that gets a huge integer $ n $ from the input and tells what is the $ n $ -th even-length positive palindrome number?

输入输出格式

输入格式

The only line of the input contains a single integer $ n $ ( $ 1<=n<=10^{100000} $ ).

输出格式

Print the $ n $ -th even-length palindrome number.

输入输出样例

输入样例 #1

1

输出样例 #1

11

输入样例 #2

10

输出样例 #2

1001

说明

The first $ 10 $ even-length palindrome numbers are $ 11,22,33,...\ ,88,99 $ and $ 1001 $ .