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: Accepted)

import scala.collection.mutable
import scala.io.StdIn._

object Main extends App {

  val count = readInt
  val numList = readLine.split(" ").map(_.toInt)


  val set = mutable.Set.empty[Int]
  var result = "YES"

  numList.foreach { num =>
    if (set.contains(num)) {
      result = "NO"
    }
    set.add(num)
  }

  println(result)
}