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 static System.Console;
using static ConsoleApp.Util;
using static System.Math;

namespace ConsoleApp
{
    class Program
    {
       
        static void Main(string[] args)
        {
            int n = int.Parse(ReadLine());
            int[] a = ReadLine().Split().Select(int.Parse).OrderBy(x=>x).ToArray();
            for (long i = 0; i < n-1;i++)
            {
                if(a[i] == a[i+1]){
                    WriteLine("NO");
                    return;
                }



            }

            WriteLine("YES");
        }

        
    }


    static class Util{
        public static void ChMin(ref long a,long b){
            
            if(a > b){
                a = b;
            }
        }

        public static void ChMax(ref long a,long b){
            if(a < b){
                a = b;
            }
        }



		
    }
}