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: Accepted)

import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int X = sc.nextInt();
        int rX = (int)Math.sqrt((double)X);       
        
        int ans = 0;
        for(int i = 1; i <= rX; i++) {
            for(int j = 1; j <= 10; j++ ) {
                int a = (int)Math.pow( i, j );
                if( a > X ) {
                    continue;
                }
                ans = Math.max( ans, a );
            }
        }
        
        System.out.println(ans);
    }
}