import java.util.Scanner;

class Main {

    private static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        int x = sc.nextInt();
        int max = 0;
        for (int i = 1; i < 32; i++) {
            for (int j = 2; j < 10; j++) {
                int beki = (int) Math.pow(i, j);
                if (beki > x) {
                    continue;
                }

                max = Math.max(beki, max);
            }
        }
        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