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 Ruby (2.3.3) (judge verdict: Accepted)

class Array
  def uniq?
    return true if size <= 1
    s = sort
    x = s[-1] 
    s.each do |a|
      return false if x == a
      x = a
    end
    return true
  end
end

n = gets.to_s.to_i
a = gets.to_s.split.map{|i|i.to_i}

puts a.uniq? ? "YES" : "NO"