import java.util.*;
import java.io.*;
 
public class Main{
    public static void main(String[] args){
        Main m = new Main();
        m.input();
    }
 
    public void input(){
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int ans = 0;
        for(int i = 1; i <= 32; i++){
            for(int j = 2; j < 10; j++){
                if((int)Math.pow(i,j) <= a &&(int)Math.pow(i, j) > ans){
                    ans = (int)Math.pow(i,j);  
                }
            }
        }
        sc.close();
        System.out.println(ans);
    }
    
    
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz