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;

namespace abc097_b
{
    class Program
    {
        static List<int> list = new List<int>();
        static void calc()
        {
            for (int i = 2; i <= 31; i++)
            {
                for (int j = i; j <= 1000; j *= i) list.Add(j);
            }
        }
        static void Main(string[] args)
        {
            calc();
            int n = int.Parse(Console.ReadLine());
            while (!list.Contains(n)) n--;
            Console.WriteLine(n);
        }
    }
}