import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long n = scan.nextLong();
		scan.close();
		StringBuilder sb = new StringBuilder();
		long k = n % 26;
		sb.append((char)(k + 'A'));
		n = n / 26;
		while(n > 0) {
			n--;
			k = n % 26;
			sb.append((char)(k + 'A'));
			n = n / 26;
		}
		System.out.println(sb.reverse().toString());
	}
}