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# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;

class B{
  static void Main(){
            int x = int.Parse(Console.ReadLine());
 
            for (int i = x; i > 0; i--)
            {
                for(int j = 2; j <= Math.Sqrt(x);j++)
                {
                    if(i % j == 0)
                    {
                        int t = i;
                        while (t % j == 0)
                            t /= j;
 
                        if(t == 1)
                        {
                            Console.WriteLine(i);
                            return;
                        }
                    }
                }
            }
  }
}