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;

class Program {
  public static void Main() {
    int total = int.Parse(Console.ReadLine());
    long[] input = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();
    bool flag = false;
    
    Array.Sort(input);
    
    for (int i = 0; i < total - 1; i++) {
      if (input[i] == input[i + 1])
        flag = true;
    }
    
    if (flag)
      Console.WriteLine("NO");
    else
      Console.WriteLine("YES");
  }
}