import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    
    if(x>=1 && x<=1000){
      if (x == 1) {
        System.out.println(1);
        return;
      }
      int max = 1;
      for(int i = 2; i <= x; i++){
        for(int k = 2; Math.pow(i,k) <=x; k++){
          max = Math.max(max,(int)Math.pow(i,k));
         }
      }
        
        System.out.println(max);
      
    }else{
      System.out.println("入力条件が誤っています");
    } 
  }  
}
/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