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: Accepted)

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

int main(){
    int x;
  cin>>x;
  vector<int> v;
  for(int i=2; i<35; i++){
    int k=i*i;
    while(k<=1200){
      v.push_back(k);
      k *=i;
    }
  }
  v.push_back(1);
  sort(v.begin(), v.end());
  int ans=v[0];
  for(int i=0;;i++){
    if(v[i]>x) break;
    ans=v[i];
  }
cout<<ans<<endl;
}