import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        new Main().solove();
    }

    public void solove() {

        Scanner sc = new Scanner(System.in);

        int x = sc.nextInt();


        if (x == 1) {
            System.out.println(x);
            return;
        }

        int result = 2;
        
        for (int i = 2; i <= x; i++) {
            for (int j = 2; Math.pow(i, j) <= x; j++) {
                result = Math.max((int) Math.pow(i, j), result);
            }
        }
        System.out.println(result);
    }
}

/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