using System.Diagnostics;
using System.Numerics;

public class Program
{
    public static void Main()
    {

        //int num = int.Parse(Console.ReadLine() ?? string.Empty);
        string[] str = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string str = Console.ReadLine() ?? string.Empty;

        int a = int.Parse(str[0]);
        int b = int.Parse(str[1]);
        int c = int.Parse(str[2]);

        if(a == b && a == c)
        {
            Console.WriteLine(a);
        }
        else if(a != b && a != c&&b!=c)
        {
            Console.WriteLine(10-a-b-c);
        }
        else
        {
            if(a == b&& b!= c)
            {
                Console.WriteLine(c);
            }
            else if(b==c&& c!=a)
            {
                Console.WriteLine(a);
            }
            else
            {
                Console.WriteLine(b);
            }
        }

    }
}