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.Text;
using System.Threading.Tasks;
 
namespace lean {
    class Program {
        static void Main() {
            long[] a = Console.ReadLine().Split().Select(long.Parse).ToArray();
            double N = a[0];
            double kazu = 0;
            string text = "";
            for (int i = 1; i < 114514910; i++)
            {
                double rui = Math.Pow(26, i);
                if ((N-kazu) / rui < 1)
                {
                    N = N-kazu;
                    
                    for(int j = i; j > 0; j--)
                    {
                        double keta = Math.Pow(26, j);
                            if(N < keta)
                            {
                                text += "a";
                            }
                            else
                            {
                                text += "z";
                            }
                    }
                    break;
                }

                if ((N - kazu) % rui == 0 && (N - kazu) / rui == 1)
                {
                    for (int j = 0; j < i; j++)
                    {
                        text += "z";
                    }
                    break;
                }

                kazu = rui + kazu;
            }

            Console.WriteLine(text);
        }
    }
}