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.io.*; 

public class Main {
	public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     int arr[] = new int[n];
     
     for(int i = 0; i<n; i++) {
    	 arr[i] = sc.nextInt(); 
     }
     
     for(int i = 2; i<n; i++) {
    	 if(arr[i] == arr[i-2]) {
    		 System.out.println("NO"); 
    		 return ; 
    	 }
     }
     System.out.println("YES");
	}
}