import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int X = sc.nextInt();
    for(int i=X;i>0;i--){
      if(isRui(i)){
        System.out.println(i);
        return;
      }
    }
  }
  
  public static boolean isRui(int n){
     boolean res = false;
    for(int i=1;i<=n;i++){
      for(int j=2;j<12;j++){
        if(Math.pow(i,j)==n){
          return true;
        }
      }
    }
    return res;
  }
  
}
/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