CF688B.Lovely Palindromes

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?

帕里有一位朋友，他非常喜爱回文数。回文数是指正读与反读都相同的数字。例如，12321、100001 和 1 是回文数，而 112 和 1021 则不是。

帕里也正努力去喜爱回文数，但只有极少数特别且天赋异禀的人才能领悟回文数背后的美。帕里偏爱偶数长度的整数（即具有偶数位数的数字），因此她尝试观察大量具有偶数长度的大回文数（例如两位数的 11 或六位数的 122221），希望从中发现某种奥妙。

现在帕里请你编写一个程序：从输入中读取一个极大的整数 $n$，并输出第 $n$ 个偶数长度的正回文数。

The only line of the input contains a single integer n (1 ≤ n ≤ 10100 000).

输入仅包含一行，其中有一个整数 $n$（$1 \leq n \leq 10^{100\,000}$）。

Print the n-th even-length palindrome number.

输出第 n 个偶数长度的回文数。

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

前 10 个偶数长度的回文数是 $11,\,22,\,33,\,\dots,\,88,\,99$ 和 $1001$。