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: Accepted)

import static java.lang.System.*;
import java.util.*;
 
public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		int x = sc.nextInt();
		TreeSet<Integer> set = new TreeSet<>();
		set.add(1);
		for (int i=2; i<=33; i++) {
			for (int j=2; j<=100; j++) {
				if (Math.pow(i,j) > x) break;
				set.add((int)Math.pow(i,j));
			}
		}
		
		int ans = 1;
		for (Integer n: set) {
			if (n > x) break;
			ans = n;
		}
		out.println(ans);
	}
}