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Problem DMelborp Lasrever A

Reversing a string (e.g., turning "foobar" into "raboof") is pretty straightforward. In fact, most programming languages include functions or methods that, given a string, will reverse it for you. However, in this problem, you must write the code to reverse the string yourself using a recursive algorithm.

Donâ€™t worry, reversing strings recursively is very easy! Given a string $s$ with $n$ characters ($s_0s_1s_2\ldots s_{n-1}$), and a string concatenation operator ($+$), we can define a string reversal function $R$ like this:

$R(s) = \left\lbrace \begin{array}{l l} s_0 & \text {if }n=1 \\ R(s_1s_2\ldots s_{n-1}) + s_0 & \text {if }n > 1 \end{array}\right.$

When implementing your solution, you are only allowed to use the following string processing functions/methods in your programming language of choice:

• String length

• String concatenation

• Extracting a substring (including individual characters) from a given string

If there are additional functions/methods you think you would need to use, please ask a proctor about it. However, if your language of choice includes a built-in mechanism to reverse strings, you must not use it.

Your solution must use a RECURSIVE function, using the definition presented above.

On the exam, any other type of solution will receive zero points!

EVEN IF KATTIS JUDGES IT AS CORRECT!

Input

The input contains a single string. The string contains only lowercase letters, no whitespace, and has a maximum length of 50 characters.

Output

You must output a single string, which will be the reversed value of the input.

Sample Input 1 Sample Output 1
melborp
problem
Sample Input 2 Sample Output 2
lasrever
reversal
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