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 <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;

/*vector<int> p(n);
cin >> p[i]*/

int main(){

    int n;
    bool flag=false;
    cin >> n;

    vector<int> a(n);
    for(int i=0; i<n; i++) cin >> a[i];

    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            if(a[i] == a[j] && i != j) {
                flag=true;
                break;
            }
        }
        if(flag == true) break;
    }

    if(flag == true) cout << "NO" << endl;
    else cout << "YES" << endl;

    return 0;
}