using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;


class Program
{
    static void Main()
    {
        var abc = Console.ReadLine().Split().Select(int.Parse).ToList();
        var a = abc[0];
        var b = abc[1];
        var c = abc[2];

        if (a == b && b == c) 
        {
            Console.WriteLine(a);
        }
        else if(a == b || a == c)
        {
            var duplicates = abc.GroupBy(x => x).Where(x => x.Count() > 1).Select(x => x.Key).ToList();
            var result = abc.Except(duplicates).ToList();
            Console.WriteLine(String.Join("",result));
        }
        else if(a != b && b != c)
        {
            int[] abcd = {0, 1, 2, 3};
            var result = abc.Except(abcd).ToList();
            Console.WriteLine(String.Join("",result));
        }
    }
}