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.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
	    public static void main(String[] args) {
	        Scanner scan = new Scanner(System.in);
	        int num = scan.nextInt();

            List<Integer> list = new ArrayList<Integer>();
            for(int i=0; i<num; i++){
                list.add(new Integer(scan.nextInt()));
            }

            for(int i1 = 0 ; i1<list.size();i1++) {
            	for(int i2 = 0 ; i2<list.size(); i2++) {
            		if(i1 == i2) {
            			System.out.println("NO");
            			return;
            		}
            	}
            }

            System.out.println("YES");
	        scan.close();
    }
}