import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x=sc.nextInt();
        int pow;
        int ans=1;
        for(int i=2;i<=Math.sqrt(x);i++){
            pow=1;
            while(Math.pow(i, ++pow)<=x){
                ans=Math.max(ans,(int)Math.pow(i, pow));
            }
        }
        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