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: Wrong Answer)

#include <stdio.h>

int main(void)
{
	int x, a = 0, b, p, i, t;
	scanf("%d", &x);
	for (b = 1; b <= x; b++) {
		t = b;
		for (p = 2; p <= x; p++) {
			for (i = 0; i < p; i++) {
				t *= t;
				if (t <= x && a < t) a = t;
			}
		}
	}
	if (x == 1) a = 1;
	printf("%d", a);
	return 0;
}