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;

namespace Kyopuro
{
    class Program
    {
        static void Main(string[] args)
        {
            int a = int.Parse(Console.ReadLine());

            string[] str = Console.ReadLine().Split(' ');
            int[] num = new int[a];

            int i;

            bool isNG = false;


            for (i = 0; i < a; i++)
            {
                num[i] = int.Parse(str[i]);
            }


            Array.Sort(num);

            for (i = 1; i < a; i++)
            {
                if (num[i] == num[i - 1])
                {
                    isNG = true;
                }
            }


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


        }
    }
}