using System;

​

public class MainClass

{

    public static void Main()

    {

        int n = Convert.ToInt32(Console.ReadLine());

        int k=0, l=0, j=0, p=0, z=0, x=0;

        while (n!=0)

        {

        k=n%10;

        l+=k;

        n=n/10;

            while (l!=0)

        {

            j=l%10;

            p+=j;

            l/=10;

                while (j!=0)

                {

                z=j%10;

                x+=z;

                j/=10;

        }

        }

        }

        Console.WriteLine(p);

    }

}