PAT-A1041. Be Unique (20)

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
using namespace std;

#define MAX 10000+10
int a[MAX];
int vis[MAX];
int main()
{
//freopen("in.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
int N = 0;
cin >> N;
for (int i = 0; i < N; i++)
{
scanf("%d", &a[i]);
vis[a[i]]++;

}

int f = 0;
for (int i = 0; i < N; i++)
{
if (vis[a[i]] == 1)
{
printf("%d", a[i]);
f = 1;
break;
}
}
if (0 == f)
cout << "None";

return 0;
}