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>

int main(void)
{
	int X;
	int i;
	int anc = 1, test;
	
	scanf("%d", &X);
	
	if (X == 1){
		printf("1\n");
	}
	else {
		for (i = 2; i * i <= X; i++){
			test = i;
		 	while (test * i <= X){
		 		test *= i;
		 	}
		 	anc = test > anc ? test : anc;
		}
		printf("%d\n", anc);
	}
	
	return (0);
}