Design a system that takes big URLs like “http://www.geeksforgeeks.org/count-sum-of-digits-in-numbers-from-1-to-n/” and converts them into a short URL. It is given that URLs are stored in database and every URL has an associated integer id.  So your program should take an integer id and generate a URL. 

A URL character can be one of the following

1. A lower case alphabet [‘a’ to ‘z’], total 26 characters
2. An upper case alphabet [‘A’ to ‘Z’], total 26 characters
3. A digit [‘0′ to ‘9’], total 10 characters

There are total 26 + 26 + 10 = 62 possible characters.

So the task is to convert an integer (database id) to a base 62 number where digits of 62 base are "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN
OPQRSTUVWXYZ0123456789"

Example 1:

Input: 
N = 12345
Output: 
dnh
12345
Explanation: "dnh" is the url for id 12345

Example 2:

Input: 
N = 30540
Output: 
h6K
30540
Explanation: "h6K" is the url for id 30540

Your Task:  
You don't need to read input or print anything. Your task is to complete the function idToShortURL() which takes the integer n as parameters and returns an string denoting the answer.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ N ≤ 10¹⁸