Create a function that takes a string consisting of lowercase letters, uppercase letters and numbers and returns the string sorted in the same way as the examples below.
sorting("eA2a1E") ➞ "aAeE12"
sorting("Re4r") ➞ "erR4"
sorting("6jnM31Q") ➞ "jMnQ136"
sorting("846ZIbo") ➞ "bIoZ468"N/A