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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using static System.Console;
using static System.Math;

class Program {
  static void Main(string[] args) {
    int x = int.Parse(ReadLine());
    int ans = 0;
    for (int i = 1; i <= 40; i++) {
      for (int j = 2; j <= 10; j++) {
        if (Pow(i, j) <= x) ans = Max(ans,(int)Pow(i, j));
      }
    }
    WriteLine(ans);
  }
}