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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;

public class Main {
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i) == list.get(i+1)){
                count++;
            }else{}
        }

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	}
}