import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int X = sc.nextInt();
        long max = 0;
        if(X <= 3){
            System.out.println(1);
            return;
        }
        for(int i = 2;i*i <= X;i++){
            long power = i;
            while(true){
                power = power*i;
                if(power > X){
                    power = power / i;
                    break;
                }
            }
            max = Math.max(max,power);
        }
        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