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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            string[] array = Console.ReadLine().Split(' ').Select(x => x).ToArray();
            HashSet<string> hsTable = new HashSet<string>();

            //var num = int.Parse(Console.ReadLine());
            //var num2 = Console.ReadLine().Split(' ').GroupBy(a => a).ToArray().Length;
            //if (num == num2)
            //    Console.Write("YES");
            //else
            //    Console.Write("NO");



            string message = "";
            for (long j = 0; j < N; j++)
                hsTable.Add(array[j]);
            if (N == hsTable.Count)
                message = "YES";
            else
                message = "NO";
            Console.WriteLine(message);






           
        }
    }
}

//24579 =  hon
//0168 = pon
//3 = bon
//long n = long.Parse(Console.ReadLine());
//long[] inputLongArray = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();

//Console.WriteLine(cnt);
//Console.ReadKey();