Hi there! You have to implement the

String get_column_title(int num) // syntax depends on programming language

function that takes an integer number (index of the Excel column) and returns the string represents the title of this column.

Intro

In the MS Excel lines are numbered by decimals, columns - by sets of letters.

For example, the first column has the title "A", second column - "B", 26th - "Z", 27th - "AA".

"BA"(53) comes after "AZ"(52), "AAA" comes after "ZZ".

Excel? Columns? More details here

Input

It takes only one argument - column decimal index number. Argument num is a natural number.

Output

Output is the upper-case string represents the title of column. It contains the English letters: A..Z

Errors

For cases num < 1 your function should throw/raise IndexError. In case of non-integer argument you should throw/raise TypeError.

In Java, you should throw Exceptions.

Nothing should be returned in Haskell.

Examples

Python, Ruby:

>>> get_column_title(52)
"AZ"
>>> get_column_title(1337)
"AYK"
>>> get_column_title(432778)
"XPEH"
>>> get_column_title()
TypeError:
>>> get_column_title("123")
TypeError:
>>> get_column_title(0)
IndexError:

JS, Java:

>>> getColumnTitle(52)
"AZ"
>>> getColumnTitle(1337)
"AYK"
>>> getColumnTitle(432778)
"XPEH"
>>> getColumnTitle()
TypeError:
>>> getColumnTitle("123")
TypeError:
>>> getColumnTitle(0)
IndexError:

Hint

The difference between the 26-digits notation and Excel columns numeration that in the first system, after "Z" there are "BA", "BB", ..., while in the Excel columns scale there is a range of 26 elements: AA, AB, ... , AZ between Z and BA.

It is as if in the decimal notation was the following order: 0, 1, 2, .., 9, 00, 01, 02, .., 09, 10, 11, .., 19, 20..29..99, 000, 001 and so on.

Also

The task is really sapid and hard. If you're stuck - write to the discussion board, there are many smart people willing to help.