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 System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC097B
{
    class Program
    {
        static void Main(string[] args)
        {
            int X, b = 1, p = 2;
            double  max=0;
            X = int.Parse(Console.ReadLine());
            if(X==1)
            {
                max = 1;
            }
            for (b = 2; b*b<=X; b++)
            {
                for(p=2;Math.Pow(b,p)<=X;p++)
                {
                     if(Math.Pow(b,p)<=X&&max<Math.Pow(b,p))
                    {
                        max = Math.Pow(b, p);
                    }
                }
            }
            Console.WriteLine(max);
            Console.ReadKey();

        }
    }
}