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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.*

fun main(args : Array<String>) {
    val n = readLine()!!.toInt()
    val aa = readLine()!!.split(" ").map { it.toInt() }
    val bb = HashMap<Int, Int>()

    aa.forEach {
        bb[it] = (bb[it] ?: 0) + 1
        if (bb[it]!! > 1) {
            println("NO")
            return
        }
    }

    println("YES")
}