import java.util.*;

public class Main{
    public static void main(String[]args){
        Scanner sc=new Scanner(System.in);
        int x=sc.nextInt();
        int max=0;
        
        for(int i=1;i<=1000;i++){
            for(int k=2;k<=1000;k++){
                if((int)Math.pow(i,k)>x) break;
                if((int)Math.pow(i,k)>max){
                    max=(int)Math.pow(i,k);
                }
            }
        }
        System.out.println(max);
    }
}
/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