import java.util.*;

public class Exercise36{
  public static void main (String[] args){

    Scanner sc = new Scanner(System.in);

    long number = sc.nextLong();

    String[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");

    String answer = getAlphabets(number, alphabet);

    System.out.println(answer);
  }

  private static String getAlphabets(long number, String[] alphabet){
    long b = number % 26;

    if (number / 26 == 0){
      return alphabet[(int)b];
    }else{
      return getAlphabets(number / 26 - 1, alphabet) + alphabet[(int)b];
    }
  }
}