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)

// g++ -std=gnu++1y -O2 xxx.cpp

#include <bits/stdc++.h>

using namespace std;

using ll = long long;

int main() {
    ll N; cin>>N;
    map<ll, ll> m;

    ll A;
    for (int i=0;i<N;i++) {
        cin >> A;
        m[A]++;

        if (m[A] > 1) {
            cout << "NO" << endl;
            return 0;
        }
    }

    cout << "YES" << endl;

    return 0;
}