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: Accepted)

#include <iostream>
#include <cstring>
#include <math.h>
#include <algorithm>
#include <cstdio>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <set>
#define ll long long
const int N = 1e6 + 10;
using namespace std;
int n;
int t;
set<int> s;
int main() {
  ios::sync_with_stdio(false);
  cin>>n;
 for(int i=0;i<n;i++){
      cin>>t;
      s.insert(t);
  }
  int ans=s.size();
  if(ans==n)  cout<<"YES"<<endl;
  else cout<<"NO"<<endl;
    return 0;
}