import java.util.Scanner;

public class Main {

	public static void main (String[] args) {

		Scanner sc = new Scanner(System.in);

		System.out.println(solve(sc.nextInt()));

		sc.close();

	}

	public static String solve (int n) {
		String[] alp = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
		String ret = alp[n % 26];

		n /= 26;

		if (n == 0) return ret;

		while (n != 0) {
			ret = alp[n % 26 - 1] + ret;
			n /= 26;
		}

		return ret;
	}

}