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

#define _CRT_SECURE_NO_WARNINGS

int main(int argc, char const *argv[])
{
	int x,exp[1003];
	int b;
  
	exp[1] = 1;
	scanf("%d",&x);
	for (int i = 2; i <= x; ++i)
	{
		b = i * i;
		while(b <= x){
			exp[b] = 1;
			b *= i;
		}
	}
	for (int i = x; i >= 1 ; --i)
	{
		if(exp[i]){
			printf("%d\n", i);
			return 0;
		}
	}
}