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;

public class Program
{
    public static void Main(string[] args)
    {
        string ans = "YES";
        int n = int.Parse(Console.ReadLine());
        string[] inputs = Console.ReadLine().Split(' ');
        long[] lis = new long[n];
        for(int i=0; i<n;i++)
        {
            lis[i] = long.Parse(inputs[i]);
            for (int j = 0; j < i; j++)
            {
                if (lis[i] == lis[j])
                {
                    ans = "NO";
                    break;
                }
            }
        }

        //出力
        Console.WriteLine(ans);
    }
}