#include<iostream>
using namespace std;
int main()
{
	int n;
	while (cin >> n)
	{
		int a[10005] = { 0 };
		int time[10005] = { 0 };
		for (int i = 0; i < n; i++)
		{
			int temp;
			cin >> temp;
			if (a[temp] == 0)
			{
				a[temp] = 1;
				time[temp] = i;
			}

			else a[temp] = -1;
		}
		int early = 999999,num=-1;
		for (int i = 0; i < 10005; i++)
		{
			if (a[i] == 1 && time[i] < early)
			{
				early = time[i];
				num = i;
			}
		}
		if (num==-1)cout << "None\n";
		else cout <<num<< endl;
	}
	return 0;
}