import java.util.*;

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

        int X = sc.nextInt();
        double max = 0;

        if(X==1){
            System.out.println(1);
        }
        else{
            for(int i=1; i<40; i++){
                for(int j=2; j<=10; j++){
                    if(Math.pow(i, j)<=X){
                        max = Math.max(max, Math.pow(i, j));
                    }
                    else{
                        break;
                    }
                }
            }
            System.out.println((int)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