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.*;
public class Main {

	public static void main(String[] args) {
		Scanner  sc = new Scanner(System.in);
		// input
		int n = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for(int i=0; i<n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		// judge
		for(int i=0; i<n; i++) {
			for(int j=i+1; j<n; j++) {
				if(a[i] == a[j]) {
					System.out.println("NO");
					return;
				}
			}
		}
		System.out.println("YES");
	}
}