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.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace AC
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = ReadLong();
            const long num = 26;
            var digit = 1;
            while (N > Math.Pow(num, digit)) digit++;
            var rem = N;
            var sb = new StringBuilder();
            for (int i = 0; i < digit - 1; i++)
            {
                var dif = (long)Math.Pow(num, digit - (i + 1));
                var cnt = 1;
                for (char c = 'a'; c <= 'z'; c++)
                {
                    if (rem >= dif * cnt + 1 && rem <= dif * (cnt + 1))
                    {
                        sb.Append(c);
                        rem -= dif * cnt;
                        break;
                    }
                    else
                    {
                        cnt++;
                    }
                }
            }
            var last = 1;
            for (char c = 'a'; c <= 'z'; c++)
            {
                if (rem == last)
                {
                    sb.Append(c);
                    break;
                }
                else last++;
            }

            Console.WriteLine(sb.ToString());
            Console.ReadLine();
        }

        static string Read() { return Console.ReadLine(); }
        static int ReadInt() { return int.Parse(Read()); }
        static long ReadLong() { return long.Parse(Read()); }
        static string[] ReadArrayString() { return Read().Split(' '); }
        static int[] ReadArrayInt() { return Read().Split(' ').Select(s => int.Parse(s)).ToArray(); }
        static long[] ReadArrayLong() { return Read().Split(' ').Select(s => long.Parse(s)).ToArray(); }
    }
}