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.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main{

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ

		Scanner scanner = new Scanner(System.in);
	    //String input1 = scanner.next();
	    String input2 = scanner.next();

	    //int h=Integer.parseInt(input1);
	    int n=Integer.parseInt(input2);
	    int a[]=new int[n];
	    Set<String> sa=new HashSet<String>();
	    for(int i=0;i<n;i++) {
	    	if(!sa.add(scanner.next())) {
	    		System.out.println("NO");
	    		return;
	    	}
	    }
	    scanner.close();
	    int sum=sa.stream()
	    		.mapToInt(s->Integer.parseInt(s))
	    		.sum();
	    	System.out.println("YES");
	}

}