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 C# (Mono 4.6.2.0) (judge verdict: Time Limit Exceeded)

using System;
class Program
{
	static void Main(string[] args)
	{
		int a = int.Parse(Console.ReadLine());
		string[] input = Console.ReadLine().Split(' ');
		int b = 0;

		Array.Sort(input);

		for (int i = 1; i < a; i++)
		{
			if (input[i-1]==input[i])
			{
				b++;
				break;
			}
		}
		if (b == 0)
		{
			Console.WriteLine("YES");
		}
		else 
		{
			Console.WriteLine("NO");
		}
	}
}