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;
using System.Text;

namespace Hello
{
  class Hello
  {
    static void Main()
    {
    
      int number = int.Parse(Console.ReadLine());
      
      var p = Array.ConvertAll(Console.ReadLine().Split(' ') , int.Parse);
      
    var list = new List<int>();
      
      list.AddRange(p);
      
list.Sort((a, b) => b - a);
      
      for(int i=0;i<number-1;i++){
        
        if(list[i] == list[i+1]){
      Console.Write("NO");
      break;
      }else if(i == number-2){
      
      Console.Write("YES");
      }
        
      
      }
      

      
      
      
    }
  }
}