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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>
typedef long long ll;
int main()
{
	int X, ans = 1;
	scanf("%d", &X);
	bool expo[X + 1];
	expo[1] = 1;
	for (int i = 1; i <= X; i++) {
		for (int j = 2; j <= X; j++) {
			int tmp = pow(i, j);
			if (tmp <= X && tmp > ans)
				ans = tmp;
		}
	}
	printf("%d\n", ans);
	return 0;
}