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 A{
  static void Main(){
    int X = int.Parse(Console.ReadLine());
    int Temp = 0, ans = 0;

    for (int i = X;0 < X ; i--){
      Temp = i * i;
      if (Temp >= X){
        if (i - 1 == 0){
          ans = i * i;
        }
        else{
        ans = (i-1) * (i-1);
        }
        break;
      }
    }
    Console.WriteLine(ans);
  }
}