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.*;

class Main{
	static Scanner s=new Scanner(System.in);
	static int gInt(){
		return Integer.parseInt(s.next());
	}
	public static void main(String[] A){
		int a=gInt();
		long r=1;
		for(int i=2;i<a;++i){
			long v=i*i;
			if(v<=a){
				while(v*i<=a)
					v*=i;
				r=Math.max(r,v);
			}
		}
		System.out.println(r);
	}
}