Problem:
Score : 200 points

Problem Statement

You are given a positive integer X.
Find the largest perfect power that is at most X.
Here, a perfect power is an integer that can be represented as b^p, where b is an integer not less than 1 and p is an integer not less than 2.

Constraints

1 ≤ X ≤ 1000

X is an integer.

Input

Input is given from Standard Input in the following format:

X

Output

Print the largest perfect power that is at most X.

Sample Input 1

10

Sample Output 1

9

There are four perfect powers that are at most 10: 1, 4, 8 and 9.
We should print the largest among them, 9.

Sample Input 2

1

Sample Output 2

1

Sample Input 3

999

Sample Output 3

961

Solution in Scala (2.13.1) (judge verdict: Wrong Answer)

import scala.math.sqrt

object Main extends App {
  
  val sc = new java.util.Scanner(System.in)
  val x = sc.nextInt()  
  val ans = (x to 1 by -1).find(i => sqrt(i) % 1 == 0)
  println(ans.getOrElse(-1)) 
}