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.Diagnostics;
using System.IO;
using System.Text;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Security.Policy;

class Program
{
    const string Yes = "Yes";
    const string No = "No";
    const char White = '.';
    const char Black = '#';
    const long Mod = 1000000007;

    static void Main(string[] args) {
        checked {
#if DEBUG
            MyDebugger.Test(process, "../TextFile1.txt");
            //TestCaseMaker.MakeTestCase1("../TextFile2.txt");
            //MyDebugger.Test(process, "../TextFile2.txt");
#else
            object ret = process(new StreamReader(Console.OpenStandardInput()));
            Console.WriteLine(ret);
#endif
        }
    }

    static object process(TextReader input) {
        //1000000000000001
        var n = long.Parse(input.ReadLine());

        //26進数
        var sb = new StringBuilder();

        while(n > 0) {
            var x = (n % 26);
            if(x == 0){
                x = 26;
                var c = ('a' - 1) + x;
                sb.Append((char)c);
                n /= 26;
                n /= 26;
            } else {
                var c = ('a' - 1) + x;
                sb.Append((char)c);
                n /= 26;
            }
        }

        var sb2 = new StringBuilder(sb.Length);
        for(int i=0; i<sb.Length; i++) {
            sb2.Append(sb[sb.Length-i-1]);
        }

        return sb2;
    }

    static int[] ToIntArray(string strs, int n) {
        var ret = new int[n];
        if(n == 0) return ret;
        var spl = strs.Split(' ');
        for (int i = 0; i < n; i++)
            ret[i] = int.Parse(spl[i]);
        return ret;
    }
}