Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in C++14 (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include <iostream>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#define rep(i,n) for(int i = 0; i < n;i++)
#define ll long long
#include <bits/stdc++.h>
using namespace std;
#define mo 1000000007
#define ull unsigned long long 

int main(){ 
  ll n;cin>>n;
  string s="YES";
  vector<ll>p(n);
  rep(i,n)
    cin>>p.at(i);
  for(int i=0;i<n;i++)
  {
    for(int j=i+1;j<n;j++)
    {
      if(p.at(i)==p.at(j))
      {
        s="NO";
      }
    }
  }
  cout<<s;
}