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 kotlin.system.exitProcess

fun main(args: Array<String>) {

    val n = readLine()!!.toInt()
    val a = readLine()!!.split(" ").map { it.toInt() }

    val s = a.sorted()
    for(i in 0 until n-1) {
        if(s[i] == s[i+1]) {
            println("NO")
            exitProcess(0)
        }
    }

    println("YES")
}