import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int X = sc.nextInt();
        int ans = 1;
      for (int i=2;i<=Math.floor(Math.sqrt(X));i++){
       
        int tmp = i;
        while (tmp<=X){
          if (tmp*i <= X){
            tmp *= i;
          }
          else{
            ans = Math.max(ans,tmp);
            break;
          }
        }
      }
      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