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;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            bool flag = false;
            int N;
            N = int.Parse(Console.ReadLine());

            uint[] A = new uint[N];

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

            for(int i = 0; i < N; i++)
            {
                A[i] = uint.Parse(input[i]);
            }

            /*for(int i = 0; i < N; i++)
            {
                for(int j = i + 1; j < N; j++)
                {
                    if(A[i] == A[j])
                    {
                        flag = true;
                        break;
                    }
                }

            }*/

            Array.Sort(A);

            for(int i = 0; i < N-1; i++)
            {
                if (A[i] == A[i + 1])
                {
                    flag = true;
                    break;
                }
            }

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

        }
    }
}