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 <vector>
#include <bits/stdc++.h>
#include <iomanip>
#include <iostream>
using namespace std;

int main(){
    int n,ans = 0; cin >> n;
    vector<int> vec(n);
    for(int i = 0;i < n;i++){
        cin >> vec.at(i);
    }
    sort(vec.begin(),vec.end());
    for(int i = 0;i < n-1;i++){
        if(vec.at(i) == vec.at(i+1)){
            break;
        }
        ans++;
    }
    if(ans == n-1){
        cout << "YES" << endl;
    }
    else{
        cout << "NO" << endl;
    }
}