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

namespace ABC171
{
    class C
    {
        static void Main(string[] args)
        {
            //var NK = Console.ReadLine().Split().Select(long.Parse).ToArray();
            //var p = Console.ReadLine().Split().Select(long.Parse).OrderBy(x => x).ToArray();
            // var CA = Enumerable.Repeat(0, (int)N).Select(_ => Console.ReadLine().Split().Select(long.Parse).ToArray()).ToArray();
            //var AB = Console.ReadLine().Split().Select(long.Parse).ToArray();
            long N = long.Parse(Console.ReadLine());
            char[] C = new char[26];
            C[0] = 'z';

            for (int i = 0; i < 25; i++)
            {
                C[i + 1] = (char)('a' + i);
            }
            //Console.WriteLine(string.Join(" ", C));

            string ans = "";
            //ans += C[N % 26];
            //long tempN = N / 26;
            long tempN = N;
            while (tempN > 0)
            {
                ans += C[tempN % 26];
                if(tempN % 26 == 0) tempN = tempN / 26 - 1;
                else tempN /= 26;
            }
            Console.WriteLine(string.Concat(ans.Reverse()));

        }
    }
}