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;
using System.Collections;
using System.Collections.Generic;

class Program
 {
        static void Main(string[] args)
        {
          int cnt = 0;// true
          
          int n = int.Parse(Console.ReadLine());
          
          string[] str = Console.ReadLine().Split(' ');
          
          int[] a = new int[n];
          int a_len = a.Length;
          for(int i = 0 ; i < n ; i++){
            a[i] = int.Parse(str[i]);
          }
          
          int[] a_D = a.Distinct().ToArray();
          
          //Console.WriteLine(string.Join(" ", a_D));
          if(a_len == a_D.Length){
            Console.WriteLine("YES");
          }
          else{
            Console.WriteLine("NO");
          }
        }
 }