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: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;
using static System.Console;


namespace atcorder2
{
    class Program
    {
        public static long Read()
        {

            return long.Parse(Console.ReadLine());
        }

        public static long[] Reads()
        {
            return Console.ReadLine().Split().Select(long.Parse).ToArray();
        }

       
       
        public static long gcd(long x,long y)
        {
            if (x < y) gcd(y, x);
            
            while (y > 0)
            {
                var z = x % y;
                x = y;
                y = z;
            }
            return x;
        }

        public static long lcm(long x,long y)
        {
            return x * y / gcd(x, y);
        }



        static void Main(string[] args)
        {
            var sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
            SetOut(sw);


            var n = Read();
            var m = 1;
            var memo = n;
            
            var ans = new List<char>();
            while (n-(long)Math.Pow(26, m) > 0)
            {
                n -= (long)Math.Pow(26,m);
                m++;
            }
            
            n--;
            for (int i = 0; i < m; i++)
            {
                ans.Add((char)('a' + n  % 26));
                n /= 26;
            } 
            

            
         
              
            
            var str = "";      
            for (int i = 0; i < ans.Count; i++)
            {
                str = ans[i].ToString() + str;
            }
            WriteLine(str);
          
            Out.Flush();
        }
    }
}