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.Linq;

public class Hello{
    public static void Main(){
        var n = int.Parse(Console.ReadLine());
        var a=Console.ReadLine().Trim().Split().Select(int.Parse).ToArray();
        var ans=true;
        for(var i=0;i<n;i++){
            for(var j=i+1;j<n;j++){
                if(a[i]==a[j]){
                    ans=false;
                    break;
                }
            }
        }
        System.Console.WriteLine(ans?"YES":"NO");
    }
}