import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {
            long n = Long.parseLong(scan.next());
            n++;
            String ans = "";
            while(n > 0) {
                n--;
                ans = (char)(n % 26 + 'A') + ans;
                n /= 26;
            }
            System.out.println(ans);
        }
    }
}