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


class Program
{
   
    public static long Read()
    {
        return long.Parse(Console.ReadLine());
    }

    public static long[] Reads()
    {
         return Console.ReadLine().Split().Select(long.Parse).ToArray();
    }
  
     public static int digit(long x)
    {
        int d = 0;
        if (x == 0)
            return 1;
        else
        {
            while (x > 0)
            {
                x /= 10;
                d++;
            }
            return d;
        }
    }
    public static void Main(string[] args)
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        
        var n = Read();
        var input = Reads();
        var a = new long[n];
        for(long i = 0; i < n; i++)
        {
            a[i] = input[i];
        }
        Array.Sort(a);
        bool f = false;
        for(long i = 0; i < n-1; i++)
        {
            if (a[i] == a[i + 1])
            {
                f = true;
            }
        }
        if (f)
            Console.WriteLine("NO");
        else
            Console.WriteLine("YES");
        

      
        Console.Out.Flush();

    }
}