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 <bits/stdc++.h>
using namespace std;

int main(){
    int X; cin>>X;
    int ans = 1;
    if(X == 1){
        cout << 1 << endl;
        return 0;
    }
    for(int i=2;i<=X;i++){
        int tmp = i;
        int tmp2 = i;
        while(tmp<=X){
            tmp *= tmp2;
            if(X>=tmp) ans = max(tmp,ans);
        }
    }
    cout << ans<<endl;

    return 0;
}