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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.Scanner;
import java.util.Arrays;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		long a[] = new long[N];
		
		for(int i=0;i<N;i++) {
			a[i] = sc.nextLong();
		}

		
		Arrays.parallelSort(a);		
		for(int j=0;j<N-1;j++) {
			if(a[j]-a[j+1]==0) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
//		for(int i=0;i<N-1;i++) {
//			for(int j=i+1; j<N; j++) {
//	//			System.out.println("ai:"+a[i]);
//	//			System.out.println("aj:"+a[j]);
//
//				if(a[i]==a[j]) {
//					System.out.println("NO");
//					return;
//				}
//			}
//		
//		}
//		System.out.println("YES");
		

	}	
}