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;
class Program
{
    static void Main(string[] args)
    {
        int X = int.Parse(System.Console.ReadLine());
        int a = 0;
        int b = 0;
        int c = 0;

        for(int i = 0; i < 1001; i++)
        {
            b++;
            int d = b;
            for (int j = 0; j < 10; j++)
            {
                c = d * d;
                if (c > a && c <= X)
                {
                    a = c;
                }
                if (c > X) { break; }
                d++;

            }
        }
        Console.WriteLine(a);

    }
}