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# (Mono-mcs 6.8.0.105) (judge verdict: Accepted)

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

class Program
{
    static void Main(string[] args)
    {
        var N = decimal.Parse(Console.ReadLine()) - 1;

        var list = new List<decimal>();

        var i = 1;

        var current = N;

        while (true)
        {
            if ((i != 1 && current / 26 > 1) || (i == 1 && current/ 26 >= 1))
            {
                if (i == 1 || current % 26 != 0)
                {
                    list.Add(current % 26);
                }
                else
                {
                    list.Add(26);
                }
                var div = (current % 26 == 0 ? 26 : current % 26);
                if(i == 1)
                {
                    div = current % 26;
                }

                current = (current - div) / 26;
            }
            else
            {
                if (i == 1 || current % 26 != 0)
                {
                    list.Add(current % 26);
                }
                else
                {
                    list.Add(26);
                }
                break;
            }
            i++;
        }

        var ans = "";

        for(var j = list.Count - 1; j > -1; j--)
        {
            var n = 97;
            if(j != 0) {
                n -= 1;
            }
            ans += (char)(list[j] + n);
        }

        Console.WriteLine(ans);
        Console.ReadLine();

    }
}