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)

import scala.io.StdIn.readLine

object Main extends App {

  val Array(n, k) = readLine().split(" ").map(_.toInt)
  val xs = readLine().split(" ").map(_.toDouble)
  val ys =
    xs.sliding(k)
      .foldLeft(Array(0d))((max, zs) => if (zs.sum > max.sum) zs else max)

  val s = ys.map(z => (z * (1 + z) / 2) / z).sum

  println(s)
}