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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

# include "cstdio"

using namespace std;

const int maxm=1000+10;

int n; 

bool f[maxm];

int main(){
	f[1]=true;
	register int i,j;
	for(i=2;i<1000;i++){
		for(j=i*i;j<1000;j*=i){
			f[j]=true;
		}
	}
	scanf("%d",&n); 
	for(i=n;i>=1;i--){
		if(f[i]){
			printf("%d",i);
			return 0; 
		} 
	}
	return 0;
}