Given a positive integer A, return its corresponding column title as appear in an Excel sheet.
1 <= A <= 1000000000
First and only argument is integer A.
Return a string, the answer to the problem.
A = 1
A = 28
1 -> A
1 -> A 2 -> B 3 -> C ... 26 -> Z 27 -> AA 28 -> AB
NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a question? Checkout Sample Codes for more details.