import java.util.Scanner;


public class Main {
	
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        
        long X = sc.nextLong();
        long max = 1;
        
        for(long i=2;i*i<=X;i++){
        	
        	long pow = i*i;
        	
        	for(;pow<=X;pow *= i)
        		if(max<pow)
        			max = pow;
        	
        }
        
        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