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: Time Limit Exceeded)

import java.util.Scanner;

public class Main {
  
	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();

		int[] a = new int[N];
		//long a1 = sc.nextLong();

		boolean ans = true;

		/*
		for(int i=0;i<N;i++){
			a[i] = sc.nextInt();
		}
		*/

		//a[0] = sc.nextInt();

		for(int i=0;(i<N)&&(ans);i++){
			a[i] = sc.nextInt();
			
			for(int j=0;j<i;j++){

				if(a[i] == a[j]){
					ans = false;
					break;
				}
			}
		}

		if(ans){
			System.out.println("YES");
		}
		else{
			System.out.println("NO");
		}
	}
	
}