import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x = sc.nextInt();
        int g = 0;
        for (int b = 1; b <= 33; b++) {
            for (int p = 2; p <= 10; p++) {
                if ((int)Math.pow(b,p) > x) {
                    break;
                } else if ((int)Math.pow(b,p) > g){
                    g = (int)Math.pow(b,p);
                }
            }
        }
        System.out.print(g);
        sc.close();
    }
}
/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