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.Generic;


    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            string[] input = Console.ReadLine().Split(' ');
            int[] A = new int[N];
            for(int i=0; i<N; i++){
                A[i] = int.Parse(input[i]);
            }

            string different = "YES";
            /*
            bool quit = false;

            for(int i=0; i<N-1; i++){
                for(int j=i+1; j<N; j++){
                    if(A[j]==A[i]){
                        different = "NO";
                        quit = true;
                        break;
                    }
                }
                if(quit==true) break;
            }
            */

            if(A.Length == A.Distinct().Count()){
                different = "YES";
            }else{
                different = "NO";
            }

            Console.WriteLine(different);
        }
    }