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.Collections.Generic;
using System.Linq;
 
class CDistinctorNot {
    static void Main(string[] args) {
        int n = int.Parse(System.Console.ReadLine());
        int[] alist = Console.ReadLine().Trim().Split(' ').Select(a => int.Parse(a)).ToArray();
        Array.Sort(alist);
        bool rtn = true;
        int wk = 0;
        for (int i = 0; i < n; i++){
            if (wk == alist[i]) {
                rtn = false;
                break;
            }
            wk = alist[i];
        }
        if (rtn) {
            System.Console.WriteLine("YES");
        } else {
            System.Console.WriteLine("NO");
        }
    }
}