import java.util.*;


public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int X = sc.nextInt();
    int expMax = 1 ;

    for(int i = 2 ; i <= Math.sqrt(X); i ++){
      int index = 1 ;
      int exp = i;
      int expWork = exp;
      while(expWork <= X){
        if(expMax < expWork){
          expMax = expWork;
        }
        expWork = expWork * exp ;
        index ++ ;
      }
    }

    System.out.println(expMax);
  }
}

/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