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.Linq;

namespace ABC154_C
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int[] A = Console.ReadLine().Trim().Split(' ').Select(a => int.Parse(a)).ToArray();
            Array.Sort(A);
            for (int i = 0; i < N - 1; i++)
            {
                if (A[i] == A[i + 1])
                {
                    Console.WriteLine("NO");
                    Environment.Exit(0);
                }
            }
            Console.WriteLine("YES");
        }
    }
}