import java.util.Scanner;

public class Test {
	public static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		long n = sc.nextLong();
		String s = "";
		s += (char) ('A' + (n % 26));
		n /= 26;
		while (n > 0) {
			if (n % 27 > 0) {
				s = (char) ('A' + (n % 27) - 1) + s;
			}
			n /= 27;
		}
		System.out.println(s);
	}
}