// editor1
import java.util.Scanner;
public class Main
{
    static String numberToTitle(int n)
    {
        if(n<=0) return"Invalid input";
        StringBuilder sb=new StringBuilder();
        while(n>0)
        {
            n--;
            sb.insert(0,(char)('A'+n%26));
            n/=26;
        }
        return sb.toString();
    }
    public static void main(String[] args)
    {
        Scanner sc=new Scanner(System.in);
        int n=sc.hasNextInt()? sc.nextInt():-1;
        System.out.println(n>0? numberToTitle(n):"Invalid input");
    }
}