import java.util.Scanner;

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

		Scanner sc=new Scanner(System.in);
		int X=sc.nextInt();
		int ans=1;
		for(int i=2;i*i<=X;i++) {
			for(int j=i*i;j<=X;j*=i) {
				ans=Math.max(ans,j);
			}
		}
		System.out.println(ans);
		sc.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