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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
import java.io.*;

public class Main {
		public static void main(String[] args) throws IOException {
		
		// 入出力高速化 java.io.* とthrows IOExceptionを忘れずに
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int[] B = new int[32];
		for(int b=0; b<32; b++){
			B[b]=(b+1)*(b+1);
		}
		
		int X = Integer.parseInt(br.readLine());
		int ans = 0;
		for(int x=0; x<32; x++){
			if(B[x]>X){
				ans = B[x-1];
				break;
			}
		}
		
        System.out.println(ans);
    }
}