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++ (Clang 10.0.0) (judge verdict: Wrong Answer)

#include<iostream>
#include<string>
#include<iomanip>
#include<algorithm>
#include<queue>
#include<math.h>
#include<vector>
#include<map>
#include<set>
using namespace std;
bool issqr(int n)
{
	double x = sqrt(n);
	double y = floor(x);
	if (x == y)
		return true;
	else
		return false;
}
int main()
{
	int n; cin >> n;
	for (int i = n; i >= 1; --i)
	{
		if (issqr(i)) {
			cout << i; break;
		}
	}
}