using System;
using System.Linq;

public class Program
{
	public static void Main()
	{
		var B = Console.ReadLine().Split().Select(int.Parse);
		for (int i = 1; i <= 10; i++)
		{
			if (!B.Any(item => item == i))
			{
				Console.WriteLine(i);
			}
		}
	}
}