import java.util.Scanner;

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

        double X = scanner.nextDouble();

        double doubleSqrt = Math.sqrt(X);
        int sqrt = (int) Math.floor(doubleSqrt);

        int ans = 1;

        if (sqrt<2){
            System.out.println(ans);
            return;
        }

        for (int i = 2; i <= sqrt; i++) {
            int accum = i;
            while (true){
                accum*=i;
                if (accum>X){
                    break;
                }
                if (ans<accum) ans = accum;
            }
        }
        System.out.println(ans);

        scanner.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