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

int main(void)
{
	int X;
	int  b, p, max = 0;

	scanf("%d", &X);

	if (X == 1) {
		printf("1\n");
		return 0;
	}
	else {
		for (b = 2; b < X; b++) {
			for (p = 2; pow((double)b, (double)p) < (double)X; p++) {
				//printf("%d %d %d \n", b, p, (int)pow((double)b, (double)p));
				if ((int)pow((double)b, (double)p) < X && (int)pow(b, p) > max)
					max = (int)pow(b, p);
			}
		}

		//printf("%d %d %d \n", b, p, (int)pow((double)b, (double)p));
		printf("%d\n", max);
		//printf("%d %d %d", abs(a - b), abs(b - c), abs(a - c));

		return 0;
	}
}