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)

# 整数列 A1,A2,...,AN が与えられます。 
# この整数列のどの 2 つの要素も互いに異なるならば YES を、そうでないなら NO を出力してください。

n = gets.to_i
a = gets.chomp.split
n.times do |i|
    a[i] = a[i].to_i
end

a.sort!

result = true
(n - 1).times do |i|
    if a[i] == a[i + 1]
        result = false
        break
    end
end

puts result ? "YES" : "NO"