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 Java7 (OpenJDK 1.7.0) (judge verdict: Accepted)

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int X=sc.nextInt();
		int a=1;
		if(X==1) {
			System.out.println(a);
			System.exit(0);
		}
		for(int i=2;i*i<=X;i++) {
			for(int k=1;(int)Math.pow(i, k)<=X;k++) {
				if((int)Math.pow(i, k)>a) {
					a=(int)Math.pow(i, k);
				}
			}
		}
		System.out.println(a);
	}
}