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 <bits/stdc++.h>
using namespace std;

int main()
{
    // string S;
    // cin >> S;
    // int i;
    // for(i=0; i < S.length(); i++){
    //   cout << "x";
    // }
    int N;
    int i;
    string ans = "YES";
    cin >> N;
    vector<int> A(N);
    for(i = 0; i < N;i++){
      cin >> A.at(i);
    }
    sort(A.begin(),A.end());
    for(i = 0; i < N-1;i++){
      if(A.at(i) == A.at(i+1)){
        ans = "NO";
        break;
      }
    }
    cout << ans;
}