Problem Description

You have been asked to create a program that takes a 3-digit integer as input and outputs its double.

However, it seems that the input string $ S $ may sometimes contain lowercase English letters. Therefore, in such cases, you decided to output an error.

Create a program that outputs the double of the value if $ S $ is a 3-digit integer (including cases that start with 0), and outputs error otherwise.

Input Format

The input is given from the standard input in the following format:

$ S $

Output Format

Output an integer or the string error as instructed in the problem statement.

Sample Input and Output

Sample Input #1

678

Sample Output #1

1356

Sample Input #2

abc

Sample Output #2

error

Sample Input #3

0x8

Sample Output #3

error

Sample Input #4

012

Sample Output #4

24

Notes/Hints

Constraints

• $ S $ is a string of length 3.
• Each character of $ S $ is either a digit or a lowercase English letter.

Sample Explanation 1

Since an integer is given, output its double.

Sample Explanation 2

Since a non-integer is given, output error.

Sample Explanation 3

There may be cases where a mix of digits and lowercase English letters is given. Also, depending on the language, even if the string is interpretable as an integer, output error.

Sample Explanation 4

Note that if $ S $ starts with 0, it should still be treated as a decimal integer.

见题面 Input 部分

见题面 Output 部分