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;

namespace atcoder097_B
{
    class Program
    {
        static void Main(string[] args)
        {
            //入力を受け取る
            int X = int.Parse(Console.ReadLine());

            //最終的に出力する変数
            int result = 0; ;

            //1000までのべき定数を作成
            int[] Beki = new int[350];
            int cnt = 0;
            for (int i = 1; i < 33; i++)
            {
                for (int j = 2; j < 9; j++)
                {
                    Beki[cnt] = (int)Math.Pow(i, j);
                    cnt++;
                }
            }

            //X以下で最大のべき乗数を探す
            for (int i = X; i > 0; i--)
            {
                for (int j = 0; j < 350; j++)
                {
                    if (i == Beki[j])
                    {
                        result = Beki[j];
                        goto last;
                    }
                }
            }

            last:;
            Console.WriteLine(result);
        }
    }
}