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;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TOPSIC
{
    partial class Program
    {
        static void Main(string[] args)
        {
          string ans = "YES";

            int N = int.Parse(Console.ReadLine());

            string[] A = Console.ReadLine().Split(' ');
            //int[] A = new int[N];
            //for (int i = 0; i < N; i++)
            //{
            //    A[i] = int.Parse(inputStr[i]);
            //}

            for (int i = 0; i < N; i++)
            {
                for (int j = i + 1; j < N; j++)
                {
                    if (A[i] == A[j])
                    {
                        ans = "NO";
                    }
                }
            }


            Console.WriteLine(ans);


        }
    }
}