import java.io.IOException;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws IOException {

        // long startTime = System.currentTimeMillis();

        Scanner scanner = new Scanner(System.in);

        int x = scanner.nextInt();

        scanner.close();

        System.out.println(calc(x));

        // System.out.println(System.currentTimeMillis() - startTime);
    }

    private static int calc(int x) {
        int s = (int) Math.sqrt(x);
        int max = 1;
        for (int i = 2; i <= s; i++) {
            int j = i;
            int k = 2;
            while (j <= x) {
                if (max < j) {
                    max = j;
                }
                j = (int) Math.pow(i, k);
                k++;
            }
        }

        return 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