import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    ArrayList<Integer> expo = new ArrayList<>();
    for (int b = 1; b <= 1000; b++) {
      int tmp = b;
      for (int p = 2; p <= 9; p++) {
        tmp *= b;
        if (tmp <= x) {
          expo.add(tmp);
        }
      }
    }
    Collections.sort(expo);
    System.out.println(expo.get(expo.size() - 1));
  }
}
/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