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: Runtime Error)

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

int note[1001];
int x;

int main() {
	scanf("%d", &x);

	for(int i = 1; i <= 40; i++) {
		for(int j = 2; j <= 10; j++) {
			int temp = pow(i, j);
			if(temp > 1000) {
				continue;
			}
			note[temp] = 1;
		}
	}

	int last = 1;
	for(int i = 0; i <= x; i++) {
		if(note[i] == 1) {
			last = i;
		}
	}

	printf("%d\n", last);
	return 0;
}