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: Time Limit Exceeded)

    fun main(args: Array<String>) {
        val n = readLine()!!
        val alist = readLine()!!.split(" ").map { it.toInt() }
        var yes = false
        alist.forEach { 
            if (alist.filter { a -> a == it }.count() >= 2) {
                yes = true
            }
        }
        if (!yes) {
            print("YES")
        } else {
            print("NO")
        }
    }