import java.util.Scanner;
import java.util.TreeSet;
 
public class Main {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		
		TreeSet<Integer> expo = new TreeSet<>();
		expo.add(1);
		for(int i = 1; i <= x; i++) {
			for(int n = 2; n < x; n++) {
				double result = Math.pow((double)i,(double)n);
				if(result > x) {
					break;
				}else {
					expo.add((int)result);
				}
			}
		}
		
		System.out.println(expo.last());
	}
}
/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