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

    for (i in 2..Int.MAX_VALUE) {
        if (pow(i, 2) > X) {
            break
        }
        for (j in 1..Int.MAX_VALUE) {
            if (pow(i, j) > X) {
                break
            }
            ans = Math.max(ans, pow(i, j))
        }
    }
    println(ans)
}

fun pow(a: Int, n: Int): Int {
    var result = 1
    repeat(n) {
        result *= a
    }
    return result
}