using System;
using System.Collections.Generic;
using System.Linq;
namespace Laino
{
class Program
static void Main(string[] args)
List<int> nums = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
int number = nums[nums.Count - 1];
while (nums.Contains(number))
nums.Remove(number);
}
Console.Write(nums[number]);
