import java.util.Scanner;
 
public class Main {
	
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int X = sc.nextInt();
        
        int max = 0;
        for (int B = 1; B < 32; B++) {
        	for (int P = 2; P < 10; P++) {
        		int pow = (int)Math.pow(B, P);
        		if (pow <= X && pow > max) {
        			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