import java.util.*;
public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    int count = 0;
    
    //x以下の間繰り返す
    for(int i = 0; i <= x; ++i){
      //1からべき乗か調べる
      for(int j = 2; j <= x; ++j){
        if((Math.pow(i,j)<= x) && (count<Math.pow(i,j))){
          count = (int)Math.pow(i,j);
        }
      }
    }
    if(count==0){
      count = 1;
    }
    System.out.println(count);
    
  }
}
/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