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: Time Limit Exceeded)

#include<iostream>
#include<cmath>
using namespace std;
int main (){
    int x,a;
    cin>>x;
    int A[x];
    for(int i=0;i<x;i++){
        A[i]=0;
    }
    for(int i=0;i<x;i++){
        for(int j=0;pow(i,j)<x;j++){
            int af=pow(i,j);
            A[af]=1;
        }
    }
    int c=0;
    for(int i=0;i<x;i++){
        if(A[i]==1){
            c=i;
        }
    }
    cout<<c+1<<endl;
}