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 Scala (2.11.7) (judge verdict: Runtime Error)

object Main extends App{
  val List(n,k) = readLine.split(" ").map(_.toInt).toList
  val p = readLine.split(" ").map(_.toDouble).toList
  
//  def ex: Double => Double = x => (x+1.0)/2.0
//  val t = p.sliding(k).map(_.map(ex)).map(_.sum).max  
  
  val t = ( p.sliding(k).map(_.sum).max + k ) / 2.0
  
  println(t)
  
}