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 ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            const string yes = "YES", no = "NO";

            string input1 = Console.ReadLine();
            string input2 = Console.ReadLine();

            var numbers = input2.Split(' ').Select(x => int.Parse(x)).ToList();

            for (int i = 0; i < numbers.Count - 1; i++)
            {
                for (int j = i + 1; j < numbers.Count; j++)
                {
                    if (numbers[i] == numbers[j])
                    {
                        Console.Write(no);
                        return;
                    }
                }
            }

            Console.Write(yes);
        }
    }
}