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-csc 3.5.0) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;
using System.Collections.Specialized;
using System.IO.Pipes;

namespace ConsoleC____
{
    
    class Program
    {
        static long beki(long a, long b)
        {
            long ans = 1;
            for (long i = 0; i < b; i++) ans *= a;
            return ans;
        }
        static void Main()
        {
            long N = long.Parse(Console.ReadLine());
            long N2 = N;
            //Console.WriteLine(N);
            long ketasu = 0;
            long i;
            char[] alphabet = new char[27];
            for (int j = 0; j < 26; j++) alphabet[j + 1] = (char)('a' + j);
            alphabet[0] = 'z';
            for (i = 26; ;i *= 26)
            {
                ketasu++;
                if (N - i > 0)
                {
                    N -= i;
                    //Console.WriteLine("N:" + N);
                    //Console.WriteLine("i:" + i);
                }
                else
                {
                    //Console.WriteLine("N:" + N);
                    //Console.WriteLine("i:" + i);
                    break;
                }
            }
            long tmp;
            //char[] ans = new char[10010];
            char[] ans = new char[ketasu];
            for (long j = ketasu - 1; j >= 0; j--)
            {
                tmp = N2 % 26;//beki(26, j);
                //Console.WriteLine(alphabet[tmp]);
                ans[j] = alphabet[tmp];
                N2 /= 26;//beki(26, j);
            }
            for (long j = 0; j < ans.Length; j++)
            {
                Write(ans[j]);
            }

        }
    }
}