import java.util.*;
import java.lang.Math;

public class Main {
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);

        int x = sc.nextInt();
        int max = 1;
        int i = 2;

        while (i * i <= x) {
            int m = i * i;
            while (m <= x) {
                if (m > max) {
                    max = m;
                }
                m *= i;
            }
            i++;
        }

        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