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.Scanner;

public class Main {

	public static void main(String[] args) {
		try (Scanner sc = new Scanner(System.in)) {
			int x = sc.nextInt();

			if (x < 3) {
				System.out.println("1");
				return;
			}

			int y = (int)Math.sqrt(x);
			int result = y * y;
			for (int i = 2; i <= y; i++) {
				int tmp = i;
				while(tmp <= x){
					tmp *= i;
				}
				tmp /= i;

				if (result < tmp) {
					result = tmp;
				}
			}

			System.out.println(result);
		}
	}
}