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 java.util.*;

public class Main {
	public static void main(String... args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int a = 0;
		for (int i = 1 ; i <= Math.sqrt(n) ; i++) {
			for (int k = 2 ; Math.pow(i, k) <= n ; k++) {
				int p = (int)Math.pow(i, k);
				if (i == 1 ) {
					a = 1;
					break;
				} else if (p <= n && p > a) {
					a = p;
				}
			}
		}
		System.out.println(a);
	}
}