Lovely Palindrome Coding Question-Codeforces rated 1000.

2 min readMay 28, 2022


Problem Statement :

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 an 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?

Input Format:

The only line of the input contains a single integer n (1 ≤ n ≤ 10¹⁰⁰⁰⁰⁰).

Output Format:

Print the n-th even-length palindrome number.

Sample Input :


Sample Output:



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


To look at even sized palindrome, we need to look at the pattern in this sequence. First even sized palindrome is 11, second 22, third 33, and so on till ninth (99). Then 10th even palindrome is a 4 digit number, 1001, 11th is 1111, 12th is 1221 & so on. Hence we might say that any n-th even palindrome is concatenation of it followed by it’s reverse.


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