import java.util.*;

public class Main{
  
  public static void main (String []args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    
    if (N == 1) { 
      System.out.println(1); return; 
    }
    
    int max = Integer.MIN_VALUE;
    for (int i = 2; i <= N; i++) {
      for (int j = 2; j <= N; j++ ){
        double pow = Math.pow((double)i, (double)j);
        if (pow > N) {
          break;
        }
        max = Math.max((int)pow, max);
      }
    }
    System.out.println(max);
  }
}
      
/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