using System;
using System.Collections.Generic;
class KaspichanNumbers
{
static void Main()
{
ulong inputN = ulong.Parse(Console.ReadLine());
string bigLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
string smallLetters = "abcdefghijklmnopqrstuvwxyz";
List<string> numbers = new List<string>(255);
int counter = 25;
for (int i = 0; i < 26; i++) numbers.Add(bigLetters[i].ToString());
for (int i = 0; i < 26; i++)
{
for (int k = 0; k < 26; k++)
{
if(counter == 256) break;
numbers.Add(smallLetters[i].ToString() + bigLetters[k]);
counter++;
}
if (counter == 256) break;
}
List<string> output = new List<string>();
if (inputN == 0) output.Add("A");
while (inputN != 0)
{
output.Add(numbers[(int)(inputN % 256)]);
inputN /= 256;
}
output.Reverse();
Console.WriteLine(String.Join("",output));
}
}