import java.util.Scanner;
class Main{
    public static void main(String arg[]){
        Scanner scn=new Scanner(System.in);
        int x =scn.nextInt();
        int answer = 0;
        if(x!=1){
            for(int i=2;i<x;i++){
                for(int j=2;;j++){
                    double buf = Math.pow(i,j);
                    if(x<buf) break;
                    if(answer<buf) answer =(int) buf;
                }
            }
    }else{
        answer = 1;
    }
        System.out.println(answer);
    }
}
/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