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

namespace debug
{
    class main
    {
        static void Main(string[] args)
        {
            //問題クラスを展開
            ProgramC a = new ProgramC();
            a.main();//実行する

        }

    }
    //ABC170
    class ProgramA
    {
        public void main()
        {
            //入力
            string s = Console.ReadLine();

            //入力が0ならその位置を答で出す
            if (s[0] > 96)
                Console.WriteLine("a");
            else
                Console.WriteLine("A");

        }
    }

    class ProgramB
    {
        public void main()
        {
            //入力
            string[] s = Console.ReadLine().Split(' ');
            int n = int.Parse(s[0]);
            int k = int.Parse(s[1]);

            string[] t = Console.ReadLine().Split(' ');
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = int.Parse(t[i]);


            Array.Sort(a);
            int ans = 0;
            for (int i = 0; i < k; i++)
                ans += a[i];

            Console.WriteLine(ans);


        }
    }

    class ProgramC
    {
        public void main()
        {

            //入力
            long n = long.Parse(Console.ReadLine());
            long n2 = n;

            List<long> list = new List<long>();
            long t = 100;

            while (n2 != 0)
            {
                n2 -= 1;
                list.Add(n2 % 26);
                n2 /= 26;
            }

            for (int i = 0; i < list.Count; i++)
            {
                Console.Write((char)(list[list.Count - 1 - i] + 'a'));
            }

        }
    }

    class ProgramD
    {
        public void main()
        {

            //入力
            long n = long.Parse(Console.ReadLine());
            string[] s = Console.ReadLine().Split(' ');
            long[] a = new long[100000];


            for (int i = 0; i < n; i++)
                a[long.Parse(s[i]) - 1]++;

            long sum = 0;

            for (int i = 0; i < n; i++)
                sum += long.Parse(s[i]);

            long q = long.Parse(Console.ReadLine());


            //それぞれの数で残るか検討
            for (int i = 0; i < q; i++)
            {
                string[] t = Console.ReadLine().Split(' ');
                sum -= a[long.Parse(t[0]) - 1] * long.Parse(t[0]);
                sum += a[long.Parse(t[0]) - 1] * long.Parse(t[1]);
                a[long.Parse(t[1]) - 1] += a[long.Parse(t[0]) - 1];
                a[long.Parse(t[0]) - 1] = 0;
                //答え出力
                Console.WriteLine(sum);


            }


        }
    }

    class ProgramE
    {

        public void main()
        {
            //入力
            int n = int.Parse(Console.ReadLine());
            string[] s = Console.ReadLine().Split(' ');
            long[] a = new long[n];

            for (int i = 0; i < n; i++)
                a[i] = long.Parse(s[i]);

            long sum = a[0] ^ a[1];

            for (int i = 2; i < n; i++)
                sum = sum ^ a[i];

            for (int i = 0; i < n; i++)
                Console.Write((sum ^ a[i]) + " ");


        }


    }

}