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)
        {
            var X = int.Parse(Console.ReadLine());

            int ans = 1;
            for(int i = 2; i < X; i++)
            {
                if (i * i > X) break;

                for (int p = 2; Math.Pow(i, p) <= X; p++)
                {
                    int now = (int)Math.Pow(i, p);
                    if (now > ans) ans = now;
                }

            }

            Console.WriteLine(ans);
            Console.ReadKey();
        }
    }
}