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-mcs 6.8.0.105) (judge verdict: Wrong Answer)

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

   public class Program
    {
        public static void Main(string[] args)
        {
            new C().test();
        }
    }

	public class C
	{
		public void test()
		{
			// N人の社員
			var inputN = CommonRead.ReadLong();

			// 1-26でa～zの変換を行わないといけない
			// n進数の変換メソッドでもいいけどね。。。
			List<long> exec = new List<long>();
			// 26以上なら繰り返す
			do
			{
				exec.Add(inputN % 26);
				inputN = inputN / 26;

			} while (inputN > 26);
			// z対策
			exec.Add(inputN % 26);


			// a-zを生成
			char[] az = Enumerable.Range('a', 'z' - 'a' + 1).Select(i => (Char)i).ToArray();
			string execStr = "";

			for (int tmp = exec.Count(); tmp > 0; tmp--)
			{
				// 1始まりのため-1
				var index = exec[tmp - 1];
				if (index == 0)
				{
					index = 25;
				}
				else
				{
					index -= 1;
				}
				execStr += az[index];
			}

			 Console.WriteLine(execStr);

		}
	}

static class CommonRead
{
    public static string ReadStr()
    {
        return Console.ReadLine();
    }
    public static string[] ReadStrA()
    {
        return ReadStr().Split(' ');
    }
    public static List<string> ReadStrL()
    {
        return ReadStrA().ToList();
    }
    public static int ReadInt()
    {
        return Convert.ToInt32(ReadStr());
    }
    public static int[] ReadIntA()
    {
        return ReadStrA().Select(s => Convert.ToInt32(s)).ToArray();
    }
    public static List<int> ReadIntL()
    {
        return ReadStrA().Select(s => Convert.ToInt32(s)).ToList();
    }
    public static long ReadLong()
    {
        return Convert.ToInt64(ReadStr());
    }
    public static long[] ReadLongA()
    {
        return ReadStrA().Select(s => Convert.ToInt64(s)).ToArray();
    }
    public static List<long> ReadLongL()
    {
        return ReadStrA().Select(s => Convert.ToInt64(s)).ToList();
    }

    public static decimal ReadDecimal()
    {
        return Convert.ToDecimal(ReadStr());
    }
    public static decimal[] ReadDecimalA()
    {
        return ReadStrA().Select(s => Convert.ToDecimal(s)).ToArray();
    }
    public static List<decimal> ReadDecimalL()
    {
        return ReadStrA().Select(s => Convert.ToDecimal(s)).ToList();
    }

    public static double ReadDouble()
    {
        return Convert.ToDouble(ReadStr());
    }
    public static double[] ReadDoubleA()
    {
        return ReadStrA().Select(s => Convert.ToDouble(s)).ToArray();
    }
    public static List<double> ReadDoubleL()
    {
        return ReadStrA().Select(s => Convert.ToDouble(s)).ToList();
    }

}