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: Runtime Error)


#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <stack>


using namespace std;

bool ans[1005];
int x;


void ss()
{
    for(int i = 1; i < 100; i++)
    {
        for(int j = 2; j < 100; j++)
        {
            int f = pow(i,j);
            if(f <= 1000)
            {
                ans[f]=1;
            }
        }
    }
}


int main()
{
    ss();
    cin >> x;
    for(int i = x; i >= 1; i--)
    {
        if(ans[i] == 1)
        {
            cout << i << endl;
            return 0;
        }
    }
    return 0;
}