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<math.h>
#include<stdlib.h>

int jo(int a, int b) {
	int i, j;
	j = a;
	for (i = 1; i < b; i++) {
		a *= j;
	}

	return a;
}

int main() {
	int i, j, k, l, m, n, x;

	scanf("%d",&x);

	m = 1;
	for (i = 2; i <= x; i++) {
		j = 2;
		k = jo(i, j);
		while (k <= x) {
			m = m < k ? k : m;
			j++;
			k = jo(i, j);
		}
	}

	printf("%d", m);

	return 0;
}