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();
		System.out.println(get(n));
	}
	public static String get(long n){
		if(n < 26){
			return ""+ (char)('A' + (n % 26));
		}
		return get(n/26 - 1) + (char)('A' + (n % 26));
	}
}