Sort Letters and Numbers

Given an alphanumeric string, the task is to separate the letters and digits, sort them individually (all letters in alphabetical order and all digits in ascending order), and then merge them into a single string by concatenating the sorted letters with the sorted digits.

For example, if the input is d3a1c2b4, after separating and sorting, the letters become abcd and the digits become 1234. The final output is abcd1234.

This problem tests your ability to manipulate strings and sort characters based on their categories.

inputFormat

The input consists of a single line containing a non-empty string s consisting of letters (both uppercase and lowercase are possible) and digits. It is guaranteed that s does not contain any spaces or other special characters.

Input Format (stdin):

string

outputFormat

Output a single string that is the result of concatenating the sorted letters followed by the sorted digits.

Output Format (stdout):

result_string

## sample

d3a1c2b4

abcd1234