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

public class Main {
	
	static boolean flg = false;
	private static final String YES = "YES";
	private static final String NO = "NO";

	public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		System.out.println("桁数を入力してください");
		int digits = scanner.nextInt();
		
		List<Integer> numberLists = new ArrayList<Integer>();
		
		for (int i = 0; i < digits; i++) {
			if (i + 1 == digits) {
				System.out.println("最後の数字を入力してください");
			}else {
				System.out.println((i+1) + "番目の数字を入力してください");				
			}
			int number = scanner.nextInt();
			numberLists.add(number);
		}
		scanner.close();
		for (int i = 0; i < numberLists.size(); i++) {
			for (int j = 0; j < numberLists.size(); j++) {
				if (i != j && numberLists.get(i) == numberLists.get(j)) {
					flg = true;
					break;
				}
			}
		}
		if (flg) {
			System.out.println(YES);
		}else {
			System.out.println(NO);
		}
	}

}