import java.util.Scanner;

public class Main {
	  
	public static void main(String args[]) {
		    Scanner scanner = new Scanner(System.in);
		    
		    int N = scanner.nextInt();
		    int bekimax = 1;
		    
		    for(int i = 2; i <= Math.sqrt(N); i++) 
		    {
		    	int beki = i * i;
		    	while( beki * i <= N ) 
		    	{
		    		beki = beki * i;
		    	}
		    	if( bekimax < beki ) 
		    	{
		    		bekimax = beki ;
		    	} 
		    }
		    System.out.println(bekimax);
		    
		    scanner.close(); }
		  }
/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