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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"math"
)

func main() {
	var x float64
	fmt.Scan(&x)

	var i, j, result float64
	result = 1

	root := math.Sqrt(x)

	for i = 2; i < root; i++ {
		j = 2
		for {
			pow := math.Pow(i, j)
			if pow > x {
				break
			}
			if pow > result {
				result = pow
			}
			j++
		}
	}
	fmt.Println(result)
}