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

namespace Main
{
    class Program
    {
        static void Main(string[] args)
        {
            //ここから
            //int n=Readint();
            //string[] str = Console.ReadLine().Split(' ');

            long n = Readlong() - 1;

            var name = new List<char>();

            long temp = n % 26;
            while (n>=0)
            {
                switch (temp)
                {
                    case 0:
                        name.Insert(0, 'a');
                        break;

                    case 1:
                        name.Insert(0, 'b');
                        break;

                    case 2:
                        name.Insert(0, 'c');
                        break;

                    case 3:
                        name.Insert(0, 'd');
                        break;

                    case 4:
                        name.Insert(0, 'e');
                        break;

                    case 5:
                        name.Insert(0, 'f');
                        break;

                    case 6:
                        name.Insert(0, 'g');
                        break;

                    case 7:
                        name.Insert(0, 'h');
                        break;

                    case 8:
                        name.Insert(0, 'i');
                        break;

                    case 9:
                        name.Insert(0, 'j');
                        break;

                    case 10:
                        name.Insert(0, 'k');
                        break;

                    case 11:
                        name.Insert(0, 'l');
                        break;

                    case 12:
                        name.Insert(0, 'm');
                        break;

                    case 13:
                        name.Insert(0, 'n');
                        break;

                    case 14:
                        name.Insert(0, 'o');
                        break;

                    case 15:
                        name.Insert(0, 'p');
                        break;

                    case 16:
                        name.Insert(0, 'q');
                        break;

                    case 17:
                        name.Insert(0, 'r');
                        break;

                    case 18:
                        name.Insert(0, 's');
                        break;

                    case 19:
                        name.Insert(0, 't');
                        break;

                    case 20:
                        name.Insert(0, 'u');
                        break;

                    case 21:
                        name.Insert(0, 'v');
                        break;

                    case 22:
                        name.Insert(0, 'w');
                        break;

                    case 23:
                        name.Insert(0, 'x');
                        break;

                    case 24:
                        name.Insert(0, 'y');
                        break;

                    case 25:
                        name.Insert(0, 'z');
                        break;
                }
                //if (n == 26) break;
                n = n/26 - 1;
                temp = (n) % 26;

            }

            foreach (char c in name) { Console.Write(c); }
            Console.WriteLine();

            //ここまで
        }

        static void Cout(string s)
        {
            Console.WriteLine(s);
            return;
        }

        static void Cout(int n)
        {
            Console.WriteLine(n);
            return;
        }

        static int Readint()
        {
            return int.Parse(Console.ReadLine());
        }

        static long Readlong()
        {
            return long.Parse(Console.ReadLine());
        }

        static int Min(int a, int b)
        {
            if (a < b) return a;
            return b;
        }

        static int Max(int a, int b)
        {
            if (a > b) return a;
            return b;
        }


    }

}


Measured memory_bytes: 27896