import java.util.*;

public class Main{
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    int res = 1;
    for(int i=2; i<x; i++){
      res = Math.max(res, getMax(x,i));
    }
    System.out.println(res);
  }

  public static int getMax(int x, int w){
    int r = w*w;
    if(r>x) return -1;
    while(r*w<=x){
      r *= w;
    }
    return r;
  }
}
/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