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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    
    if(x>=1 && x<=1000){
      if (x == 1) {
        System.out.println(1);
        return;
      }
      int max = 1;
      for(int i = 2; i <= x; i++){
        for(int k = 2; Math.pow(i,k) <=x; k++){
          max = (int)Math.pow(i,k);
         }
      }
        
        System.out.println(max);
      
    }else{
      System.out.println("入力条件が誤っています");
    } 
  }  
}