import java.util.*;

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