Problem:
Score : 300 points

Problem Statement

1000000000000001 dogs suddenly appeared under the roof of Roger's house, all of which he decided to keep. The dogs had been numbered 1 through 1000000000000001, but he gave them new names, as follows:

the dogs numbered 1,2,\cdots,26 were respectively given the names a, b, ..., z;

the dogs numbered 27,28,29,\cdots,701,702 were respectively given the names aa, ab, ac, ..., zy, zz;

the dogs numbered 703,704,705,\cdots,18277,18278 were respectively given the names aaa, aab, aac, ..., zzy, zzz;

the dogs numbered 18279,18280,18281,\cdots,475253,475254 were respectively given the names aaaa, aaab, aaac, ..., zzzy, zzzz;

the dogs numbered 475255,475256,\cdots were respectively given the names aaaaa, aaaab, ...;

and so on.

To sum it up, the dogs numbered 1, 2, \cdots were respectively given the following names:

a, b, ..., z, aa, ab, ..., az, ba, bb, ..., bz, ..., za, zb, ..., zz, aaa, aab, ..., aaz, aba, abb, ..., abz, ..., zzz, aaaa, ...

Now, Roger asks you:

"What is the name for the dog numbered N?"

Constraints

N is an integer.

1 \leq N \leq 1000000000000001

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer to Roger's question as a string consisting of lowercase English letters.

Sample Input 1

2

Sample Output 1

b

Sample Input 2

27

Sample Output 2

aa

Sample Input 3

123456789

Sample Output 3

jjddja

Solution in C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Collections.Generic;

using E = System.Linq.Enumerable;
using System.Text;

public class Program
{
    public static void Main()
    {
        var n = long.Parse(Console.ReadLine());

        var name = ExcelColumnIndexToName(n - 1);

        Console.WriteLine(name);
    }

    const int Base = 'Z' - 'A' + 1;

    // original: https://www.it-swarm.dev/ja/c%23/%E5%88%97%E7%95%AA%E5%8F%B7%EF%BC%88%E4%BE%8B%EF%BC%9A127%EF%BC%89%E3%82%92excel%E5%88%97%EF%BC%88%E4%BE%8B%EF%BC%9Aaa%EF%BC%89%E3%81%AB%E5%A4%89%E6%8F%9B%E3%81%99%E3%82%8B%E6%96%B9%E6%B3%95/958456720/
    private static string ExcelColumnIndexToName(long index)
    {
        if (index < 0)
        {
            return "";
        }

        var range = new List<char>();
        for (int i = 1; index + i > 0; i = 0)
        {
            index = Math.DivRem(index, Base, out var r);
            range.Add((char)('a' + r));
        }
        range.Reverse();
        if (range.Count > 1)
        {
            var first = range.IndexOf('a');
            for (int i = 0; i < first; ++i)
            {
                --range[i];
            }
        }

        return new string(range.ToArray());
    }
}