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.*;
 
public class Main {
 	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
		int X = sc.nextInt();
		int max = 0;

		if(X!=1){
			for(int b=2; b<Math.sqrt(X); b++){
				int p=2;
				int pow = (int) Math.pow(b,p);
				while(pow<=X){
					if(max<pow){
						max=pow;
					}
					p++;
					pow = (int) Math.pow(b,p);
				}
			}
		}else{
			System.out.println("1");
			return;
		}
		System.out.println(max);
    }
}