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;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(),(x).end()
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}


int main(){
  long long X;
  cin >> X;
  long long maxNum;
  maxNum = 1;
  for(int i = 2; i < 100; i++){
    for(int j = 2;;j++){
      long long n = pow(i,j);
      if(n <= X) maxNum = max(n,maxNum);
      else break;
    }
  }
  cout << maxNum << endl;
  return 0;
}