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();
		sb.append((char)(n % 26 + 'A'));
	    n /= 26;
		while (n > 0) {
		    n--;
		    char c = (char)(n  % 26 + 'A');
		    sb.insert(0, c);
		    n /= 26;
		}
		System.out.println(sb);
	}
}