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: Accepted)

import java.util.LinkedHashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String[] array = new String[n];
        for (int i = 0; i < n; i++) {
        	array[i] = sc.next();
        }
		int bf = 0;
		bf = array.length;;
		int af = 0;
		Set<String> linkedHashSet = new LinkedHashSet<String>();
	    for (int i = 0; i < array.length; i++) {
	        linkedHashSet.add(array[i]);
	        }

	    Object[] strings_after = linkedHashSet.toArray();
	    af = strings_after.length;

	    if(af == bf){
	    	System.out.println("YES");
	    }else{
	    	System.out.println("NO");
	    }
		}
}