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);
        
      	double num = sc.nextInt();
      	double resultx=0;
      	
      	if(num==1){
      	    System.out.println(num);
      	}
      	
      	for(int n=2; 2.0<=Math.pow(num,1.0/n);n++){
      	    double num1=Math.pow(num,1.0/n);
      	    double numfloor = Math.floor(num1);
      	    int result =(int)num1 - (int)numfloor;
      	    
      	    if(result==0){
      	        
      	        if(numfloor>resultx){
      	            resultx=numfloor;
      	             System.out.println(numfloor*numfloor);
      	        }
      	       
      	    }
      	}
      	
      	
      	
 
    }
}