import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int X=sc.nextInt();
		int a=1;
		if(X==1) {
			System.out.println(a);
			System.exit(0);
		}
		for(int i=2;i*i<=X;i++) {
			for(int k=1;(int)Math.pow(i, k)<=X;k++) {
				if((int)Math.pow(i, k)>a) {
					a=(int)Math.pow(i, k);
				}
			}
		}
		System.out.println(a);
	}
}
/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