import java.util.Scanner;
public class Main{
    public static String convert(int n){
                StringBuilder title = new StringBuilder();
        while(n>0){
            n--;
            int rem = n%26;
            title.insert(0,(char)('A'+rem));
            n/=26;
        }
        return title.toString();
    }
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        if(n<=0||!isNumeric(n)){
            System.out.print("Invalid input");
            return;
        }
        System.out.println(convert(n));
}
}