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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val x = sc.nextInt()

    println(abc097b(x))
}

private fun abc097b(x: Int): Int {
  if (x == 1) return 1

  val ansList = mutableListOf<Int>()
  for (i in 2..31) {
    var tmp = i * i 
    if (tmp > x) continue
    while (tmp < x) {
      tmp *= tmp
    }
    tmp = Math.sqrt(tmp.toDouble()).toInt()
    ansList.add(tmp)
  }
  return ansList.max()!!
}