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: Accepted)

#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define Rep(i,s,f) for(int i=(int)s;i<(int)f;i++)
using ll=long long;
using namespace std;


int main()
{
	int X;
	cin>>X;
	int ans=1;
	Rep(i,2,X)
	{
		for(int j=2;pow(i,j)<=X;j++)
		{
			ans=max(ans,(int)pow(i,j));
		}	
	}
	cout<<ans<<endl;
	return 0;
}