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++ (Clang 3.8.0) (judge verdict: Accepted)

#include <iostream>
#include <set>
using namespace std;

int main(void) {
    int N;
    cin>>N;
    set<int> s;
    for (int i = 0; i < N; i++) {
        int A;
        cin>>A;
        if (s.find(A) != s.end()) {
            cout << "NO" << endl;
            return 0;
        }
        s.insert(A);
    }
    cout << "YES" << endl;
    return 0;
}