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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.math.BigInteger;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int x = input.nextInt();

        TH:
        for (int i = x; i > 0; i--) {
            for (int j = 2; j <= i  ; j++) {
                double  nthRoot =  Math.round(Math.pow(i, 10.0/ j * 10));
                int intNthRoot = (int) nthRoot;
                if (intNthRoot == nthRoot){
                    System.out.println(i);
                    break TH;
                }
            }
            if (i == 1 ){
                System.out.println(1);
                break;
            }
        }
    }
}