1041. Be Unique

#include<iostream>
using namespace std;
int vv[10003],val[100003];
int main(){
  int n,i;cin>>n;
  for(i=0;i<n;++i)
    {cin>>val[i]; ++vv[val[i]];}
  for(i=0;i<n;++i)
    if(vv[val[i]]==1)
      {cout<<val[i]; break;}
  if(i==n)cout<<"None";
}