import java.util.Scanner;
public class Main{
    public static void main(String args[]){
        Scanner scan=new Scanner(System.in);
        int X=scan.nextInt();
        int max=1;
        int i,j;
        for(i=2;i<=Math.sqrt(X);i++){
            j=i;
            while(j*i<=X){
                j*=i;
            }
            if(max<j){
                max=j;
            }
        }
        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