using System;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        int[] x = Console.ReadLine().Split().Select(v => int.Parse(v)).ToArray();
        Array.Sort(x);
        int ans = 10;

        for (int i = 0; i < x.Length; i++)
        {
            if (i + 1 != x[i])
            {
                ans = i + 1;
                break;
            }
        }

        Console.WriteLine(ans);
        Console.ReadLine();
    }
}