package cn.itcast.algorithm.TTT_64;
import java.util.Arrays;
import java.util.Scanner;
public class Main71 {
    public static void main(String[] args) {
        //这两组为测试用例
//       int n = 7;
//       int[] nteam = {2, 2 ,1 ,3 ,3 ,3 ,1};     
//        int n = 9;
//        int[] nteam = {2, 2 ,1 ,2 ,3 ,3 ,3 ,3 ,1};
        Scanner sc = new Scanner(System.in); //开始输入有多少根筷子和每根筷子的长度
        int n = sc.nextInt();
        int[] nteam = new int[n];
        for (int j = 0;j < n;++j){
            nteam[j] = sc.nextInt();
        }
       int chang = zhaoKuaizi(n,nteam);//找出落单的筷子
       System.out.println("落单筷子的长度为：" + chang);
    }
    /**
     *找单个是利用数组排序好之后的落单不成对
     */
    private static int zhaoKuaizi(int n, int[] nteam) {
        int l = nteam.length;
        paixu(nteam);
        int m = 0;
        int i = 0;
        while(i < l){
            if(i == l-1){
                m = l-1;
                break;
            }
            if (nteam[i] == nteam[i+1]){
                i += 2;
            }else{
                m = i;
                break;
            }
        }
        return nteam[m];
    }
    /**
     * 对数组进行由大到小的排序
     *          如果怕麻烦可以用封装好的Arrays.sort();对数组进行排序
     */
    private static int[] paixu(int[] nums) {
        int max = Arrays.stream(nums).max().getAsInt();
        int min = Arrays.stream(nums).min().getAsInt();
        int[] arr = new int[max - min + 1];
        for (int num : nums) {
            arr[num - min]++;
        }
        int index = 0;
        for (int i = 0; i < nums.length; ) {
            if (arr[index] == 0) {
                index++;
                continue;
            }
            for (int j = 0; j < arr[index]; j++) {
                nums[i++] = index + min;
            }
            index++;
        }
        return nums;
    }
}