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: Accepted)

    using System;
    using System.Collections.Generic;
     
    namespace ABC171Test
    {
        class Program
        {
            static void Main()
            {
                long N = long.Parse(Console.ReadLine());
                List<char> alplist = new List<char>();
     
                for (int code = 0x61; code < 0x7b; code++) alplist.Add(Convert.ToChar(code));
     
                long S = 0;
                int k=1;
                long buf=N;
                var result = string.Empty;
                
                buf = 0;
                while (S < N) {
                    buf = S;
                    S += (long)Math.Pow(26, k);
                    k++;
                }
     
     
                long row = N - buf-1;
     
                int l=k-1;
                
                while (l > 0) {
                    long b = (long)Math.Pow(26, l-1);
                    int al = (int)(row / b);
                    row = row % b;
                    result += alplist[al];
                    l--;
                }
                Console.WriteLine(result);
                
     
     
            }
     
     
        }
     
    }