import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int X = sc.nextInt();
        int answer =1;
        
        for(int i=2; i*i<=X; i++){
            int max =i*i;
            while(max<=X){
            if(max >= answer){
                answer = max;
            }
                max *= i;
            }
        }
        
        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