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<math.h>//pow使いたいからinclude
int main() {
	int X;
	double i, j = 0;//ループ用
	double y = 1;
	scanf("%d",&X);//とりあえずXを代入

	for (i = 1; i <= X; i++) {
		for(j = 2;j <= X;j++){
			if (y < pow(i, j) && X > pow(i,j)) {
				y = pow(i, j);
			}
		}
	}

	if (X == 1) {
		printf("%d\n", X);
	}
	else {
		printf("%.0f\n", y);
	}
	return 0;
}