版权声明:// Copyright © 2018年 Coding18. All rights reserved. https://blog.csdn.net/Coding18/article/details/86320689
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int hashtable[100010] = {0};
int main()
{
int n,u;
scanf("%d",&n);
int a[n];
for(int i = 0; i < n; i++)
{
scanf("%d",&a[i]);
hashtable[a[i]]++;
}
int i;
for(i = 0; i < n; i++)
{
if(hashtable[a[i]] == 1)
{
printf("%d\n",a[i]);
break;
}
}
if(i == n) printf("None\n");
return 0;
}