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: Accepted)

import java.util.*

val sc = Scanner(System.`in`)
val X = sc.nextInt()

fun main(args: Array<String>) {
    var ans = 1

    var i = 2
    while (i * i <= X) {
        var j = i * i
        while (j <= X) {
            ans = Math.max(ans, j)
            j *= i
        }
        i++
    }

    println(ans)
}