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 <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cmath>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <string>
#include <algorithm>
#include <complex>
#include <map>
#include <vector>
#include <queue>
#include <stack>
#include <deque>
#include <list>
#include <unordered_map>

using namespace std;

int main() {
	int X;
	cin >> X;
	double tmp = std::sqrt(X);
	int val = floor(tmp);
	val = val*val;
	cout << val << endl;
}