import java.util.*;
public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int X = sc.nextInt();
    int ans = 0;
    for (int i = 2; i <= 9; i++) {
      for (int j = 0; j <= 31; j++) {
        if (X >= (int) Math.pow(j, i)) {
          ans = Math.max(ans, (int) Math.pow(j, i));
        }
      }  
    }
    System.out.println(ans);
  }
}
/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