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.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

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

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	}
}