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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Linq;

namespace testing
{
    class Program
    {

        static void Main(string[] args)
        {
            int a = int.Parse(Console.ReadLine());
            int[] b = Console.ReadLine().Split().Select(int.Parse).ToArray();
            Array.Sort(b);
            bool c = true;
            for (int i = 0; i < a - 1; i++)
            {
                if (b[i] == b[i+1]) { c = false; break; }
            }
            if (c == false) { Console.WriteLine("NO"); }
            if (c == true) { Console.WriteLine("YES"); }
        }
    }
}