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

int main(void){
    int N, Abuf;
    multiset<int> A;
    bool IfDistinct = true;

    cin >> N;
    for(int i=0; i<N; i++){
        cin >> Abuf;
        if(IfDistinct){
            if(A.find(Abuf) != A.end()){
                IfDistinct = false;
            }else{
                A.insert(Abuf);
            }
        }
    }

    if(IfDistinct){
        cout << "YES" << endl;
    }else{
        cout << "NO" << endl;
    }

    return 0;
}