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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace ABC
{
    class Program
    {
        static void Main(string[] args)
        {
            ABC097_B();
        }

        static void ABC097_B()
        {
            var X = int.Parse(Console.ReadLine());
            double ans = 1;
            for (var x = 2; x <= X; x++)
            {
                for (var i = 2; Math.Pow(x, i) < X; i++)
                {
                    ans = Math.Max(ans, Math.Pow(x, i));
                }
            }
            Console.WriteLine(ans);
        }
    }
}