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 <iostream>
#include <algorithm>
#include <vector>
#include <utility>
#include <set>
#include <cmath>
#include <string>

using namespace std;

int main(void) {
    int x,res = 0;
    cin >> x;
    for(int i = 0;i < 1000;i++) {
        for(int ii = 2;ii < 12;ii++) {
            int t = pow(i,ii);
            if(t > x)
                break;
            else
                res = max(res,t);
        }
    }
    cout << res << endl;
    return 0;
}