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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC171
{
    class Program
    {
        static void Main(string[] args)
        {
            c();
        }

        public static void c()
        {
            long n = long.Parse(Console.ReadLine());
            string ans = "";

            while (true)
            {
                
                if(n < 27)
                {
                    
                    char c = (char)(96 + n);
                    ans += c;
                    n -= 26;
                }
                else if (n % 26 != 0)
                {
                    
                    long kari = n % 26;
                    char c = (char)(96 + kari);
                    ans += c;
                    n /= 26;
                    
                }
                else if( n % 26 == 0)
                {
                    ans += "z";
                    n /= 26;
                    n--;
                }
                if (n <= 0)
                    break;
            }
            string ans1 = new string(ans.Reverse().ToArray());
            Console.WriteLine(ans1);
        }      
        //1000000000000001
        //  999999999999999
        //  200000000000000
        //  300000000000000
        //  400000000000000
        //  500000000000000
        //  600000000000000
        //  650000000000000
        //  700000000000000
        //  800000000000000
        //  900000000000000
    }
}