1041. Be Unique (20)

//#include<string>
//#include <iomanip>
#include<vector>
#include <algorithm>
//#include<stack>
#include<set>
#include<queue>
#include<map>
//#include<unordered_set>
#include<unordered_map>
//#include <sstream>
//#include "func.h"
//#include <list>
#include<stdio.h>
#include<iostream>
#include<string>
#include<memory.h>
#include<limits.h>
using namespace std;

int main(void)
{

int *frequency = new int[100001];
memset(frequency, 0, 100001 * sizeof(int));
int sum;
cin >> sum;
int *num = new int[sum];
for (int i = 0; i<sum; i++)
{
scanf("%d", &num[i]);
frequency[num[i]]++;
}
for (int i = 0; i<sum; i++)
{
if (frequency[num[i]] == 1)
{
cout << num[i] << endl;
return 0;
}
}
cout << "None" << endl;
return 0;
}