Kaspichan_2

import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String type = in.next("\\d{1,21}");
        Long n = Long.parseUnsignedLong(type);
        List<String> digits = new ArrayList<>();
        for (char i = 'A'; i <= 'Z'; i++) {
            digits.add(String.valueOf(i));
        }
        for (char i = 'a'; i <= 'i'; i++) {
            for (char j = 'A'; j <= 'Z'; j++) {
                digits.add(String.valueOf(i)+String.valueOf(j));
            }
        }
        String result = "";
        if (n==0) {
            System.out.printf("A");
        }
        while (n != 0)
        {
            result = digits.get((int) (n % 256)) + result;
            n = n /256;
        }
        System.out.printf("%s%n", result);
    }
}