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 ABCProblems
{
    class Program
    {
        static void Main(string[] args)
        {
            ///A///
            //string u;

            //string[] ab;
            //int a;
            //int b;

            //string[] st = Console.ReadLine().Split(' ');

            //string s = st[0];
            //string t = st[1];

            //ab = Console.ReadLine().Split(' ');

            //a = int.Parse(ab[0]);
            //b = int.Parse(ab[1]);

            //u = Console.ReadLine();

            //if(s == u)
            //{
            //    a--;
            //}

            //else if(t == u)
            //{
            //    b--;
            //}

            //Console.WriteLine(a + " " + b);


            ///B///
            //int s = Console.ReadLine().Length;

            //string output = "";

            //for (int i = 0; i < s; i++)
            //{
            //    output = output + "x";
            //}

            //Console.WriteLine(output.ToString());


            ///C///
            int n = int.Parse(Console.ReadLine());

            string[] input = Console.ReadLine().Split(' ');
            string[] number = new string[n];

            bool flag = false;

            for(int i = 0; i < n; i++)
            {
                number[i] = input[i];

            }


            for(int i = 0; i < n; i++)
            {
                if(flag == true)
                {
                    break;
                }

                for(int j = 0; j < i; j++)
                {
                    if(i == j)
                    {
                        continue;
                    }
                    
                    if(number[i] == number[j])
                    {
                        flag = true;
                        break;
                    }
                }
            }

            if(flag == true)
            {
                Console.WriteLine("NO");
            }
            else
            {
                Console.WriteLine("YES");
            }

        }
    }
}