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

namespace ConsoleApp1
{
    class Program2
    {
        static void Main(string[] args)
        {
            //long n = long.Parse(Console.ReadLine());
            long[] inputLongArray1 = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();
            //long[] inputLongArray2 = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();

            long input = inputLongArray1[0];
            double input2 = inputLongArray1[0];
            long temp = 0;
            long count = 1;
            var resultArray = new List<string>();

            while(input2 > 0)
            {
                var num26_double = Math.Pow(26, count);
                long num26_long = (long)num26_double;
                var num26_double2 = Math.Pow(26, count -1);
                long num26_long2 = (long)num26_double2;

                var mod = Math.Ceiling(input2 / num26_double2) % 26;

                if (mod == 0)
                {
                    resultArray.Add("z");
                }
                else if(mod == 1)
                {
                    resultArray.Add("a");
                }
                else if (mod == 2)
                {
                    resultArray.Add("b");
                }
                else if (mod == 3)
                {
                    resultArray.Add("c");
                }
                else if (mod == 4)
                {
                    resultArray.Add("d");
                }
                else if (mod == 5)
                {
                    resultArray.Add("e");
                }
                else if (mod == 6)
                {
                    resultArray.Add("f");
                }
                else if (mod == 7)
                {
                    resultArray.Add("g");
                }
                else if (mod == 8)
                {
                    resultArray.Add("h");
                }
                else if (mod == 9)
                {
                    resultArray.Add("i");
                }
                else if (mod == 10)
                {
                    resultArray.Add("j");
                }
                else if (mod == 11)
                {
                    resultArray.Add("k");
                }
                else if (mod == 12)
                {
                    resultArray.Add("l");
                }
                else if (mod == 13)
                {
                    resultArray.Add("m");
                }
                else if (mod == 14)
                {
                    resultArray.Add("n");
                }
                else if (mod == 15)
                {
                    resultArray.Add("o");
                }
                else if (mod == 16)
                {
                    resultArray.Add("p");
                }
                else if (mod == 17)
                {
                    resultArray.Add("q");
                }
                else if (mod == 18)
                {
                    resultArray.Add("r");
                }
                else if (mod == 19)
                {
                    resultArray.Add("s");
                }
                else if (mod == 20)
                {
                    resultArray.Add("t");
                }
                else if (mod == 21)
                {
                    resultArray.Add("u");
                }
                else if (mod == 22)
                {
                    resultArray.Add("v");
                }
                else if (mod == 23)
                {
                    resultArray.Add("w");
                }
                else if (mod == 24)
                {
                    resultArray.Add("x");
                }
                else if (mod == 25)
                {
                    resultArray.Add("y");
                }

                input2 -= num26_long;

                count++;
            }

            string result = string.Empty;
            resultArray.Reverse();

            foreach (var r in resultArray)
            {
                result += r;
            }

            var sw = new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            sw.Write(result);
            Console.SetOut(sw);
            Console.Out.Flush();
        }
    }
}


Measured memory_bytes: 28476