import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x = Integer.parseInt(sc.next());
        List l = new ArrayList<>();
        int max = 1;
        for(int i = 2; i <= Math.sqrt(x); i++) {
            int j = 2;
            while(true) {
                if(Math.pow(i, j) > x) break;
                if(l.contains(Math.pow(i, j)))  break;
                else {
                    if(max < Math.pow(i, j)) {
                        max = (int)Math.pow(i, j);
                    }
                }
                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