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++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);i++)
using ll=long long;
using namespace std;

int main(){
    int x;
    cin>>x;
    double num;
    bool flag=true;
    int i=0;
    int ans;
    while(flag){
        num=sqrt(x-i);
        if(ceil(num)==floor(num)){
            ans=x-i;
            flag=false;
        }
        i++;
    }
    cout<<ans<<"\n";
    return 0;
}